Brawl is looking to be great and I just -cannot- wait. As such, partly due to my own drive, partly due to the peer pressure of genus, I'm going to speculate tiers! There's nothing more fun than speculating about a new game, pushing your opinions as fact, and then finding out you were way off. As such, I'll make a tier list of all currently confirmed characters. My tier list will be based entirely off known moves, known characteristics, and ability in melee. Not favorites. Not favorites at all.
If you don't know what a tier list is, it's a list of characters n a given game with multiple character options that ranks them in order of most competitive ability to least competitive ability. Tiers are based entirely on what the most people succeed with. They are a combination of the scarcity of skilled players of that particular character and the potential of that character. For example, Marth and Sheik may be entirely broken, moving hitboxes. Despite this, however, they don't rank as the top two characters simply because, competitvely, fox wins more. Fox has more potential, speed, and shine tactics that allow him to be the best in terms of competitive odds. This doesn't mean he's the only way to go; just that he's the most competitive character, tournament wise..
So, without further delay, the predicted Super Smash Brothers Brawl tier list.
Top
Fox - Fox has crazy speed, overpowered aerials, a ridiculous upsmash, an easily spammable projectile, and, most of all, the shine. Comboing with Fox is fluent. A good fox player will always be attacking you, and there's rarely anything you can do about it. Melee proved that. Assuming nothing, little, or not enough to majorly nerf him occurs, Fox should remain atop the tier list.
Metaknight - Melee proved that being able to quickly combo your opponent is eesential to victory. Fox, Falco, Falcon, Marth, and Sheik all win because they can -quickly- attack, continue attacking, and finish off the kill. All five further demonstrate the effect speed has on gameplay. Metaknight's sword is fast. Really fast. Watch the first trailer, and you can see how quickly that thing moves. Further more, it's a disjointed hitbox (his sword can hurt you if it hits you, but you can't hurt it). He can fly, too. That's going to add a nice feature of survivability to his speed and combo potential. Watch out.
High
Zero Suit Samus - Zamus seems to be a replacement Sheik. Really. Transformation character, skinnyish build, female, heavy martial combat, occasional projectile, the plasma whip. She seems like a fast character heavily oriented towards close combat. She seems to have a very decent recovery from close, as well. I'm not sure what she'll do if she's far away.. can her up b function without a wall to grab? If so, her recovery will most likely be way up there. I just seem to see her as very Sheik like, only with a little more options from far away, and a little less ninjaesque amazingness. EDIT: Watching gameplay vids, she seems -better- than Sheik. Look at some of the playable demo vids, and you can see how ridiculous her range is. That whip is win. pure win.
Peach - From the brokenness of the downsmash to the amazing projectile that turnips were, Peach proved to be a -unique-, capable character. Peach was the only top 5 tier in melee to not be oriented towards a fast, quick strike gameplay. She was a damage racking up, turnip abusing, downsmash raping, godly recovering, prioritized arialling, floating menace. And seeing as her turnips, the best projectile int he game, return to her, she surely hasn't taken any steps in brawl to get worse. <3 Peach.
Ike - I see a heavy Marth. Less speed, more power. Probably worse than Marth if Marth returns. No real comments besides that.
Samus - Samus seems like she should be higher, doesn't she? Impossible to knock off the stage, unbelievable recovery (bombs, grapple, up b, jump), great projectiles (I'm talking to you missles), pretty powerful moves, and some nice, laid back aerials. Unfortunately, when it comes to close combat, Samus is -really- lacking. Her aerials can't/couldn't reliably be shffled, her tilts are less than amazing, and her smashes are way too long to charge.
Middle
Sonic - Well, Sonic looks really awesome. To play as, at the least. Whether or not he's great is a different question. In terms of known moves, he seems -heavily- oriented towards the spindash. This could mean plenty of things. On one side, he can easily attack from far away; on the other, however, he may lack the close combat you need to do well in smash. We don't really know aerials or tilts at all, though,so it's not really fair to judge. One thing I -can- judge is the apparently immortal recovery Sonic possesses. First off, his DI. It's ridiculous. I can't stop commenting on it. Watch the official video. He moves horizontally with such speed/ease that his air game may be like Jigglypuff's (which, if you didn't know, is almost impossible to play against). He also as a good midair spindash for horizontal distance, and huge vertical distance on that spring. Whether or not you can survive if the spindash doesn't make it or if the spring stops horizontal movement is unknown, but sonic's recovery's looking great. I can't wait to see him in good action. That down air is also unbelievable looking. What we've seen is just intense. But maybe Sakurai just wanted it that way.
Pit - Since Sakurai touted the new aerial combat emphasis, it seems very likely that a character with (appearing) multiple jumps would have an advantage. Surely having a sword would also give you an advantage. I'm kind of torn on Pit.. I want to know his smashes. What could he do? Would he be an air only character? This tier position really goes off nothing more than the fact than he has wings and a sword.
Mario - He's balanced. It's Mario. He can use aerials, has a projectile, decent recovery, all sorts of stuff. It's Mario.
Link - It's Link. Link wasn't so great in Melee.. he was slow, heavy, and had few killing options. I'm certain Sakurai wants to resurrect the second greatest nintendo star from a lifetime of doom in Smash. He's already got a new boomerang, and he may be affected by the new "heavy invincibility" rule. That's definitely enough to bring him back to a decent level.
Ice Climbers - The first significant drop. The main reason for this is because I'm goign off the idea that the wavedash is abolished. There's no reason to believe this is true or not true, so I've just predicted wavedash will be gone. I'm not really sold either way, but eh. Anyway, the Ice Climbers are slow. Their smashes, tilts and grabs are amazing. So ground movement=poor, ground attacking=great. If you are a ground char, you need ground movement. Without wavedash, ICs are screwed. You can see this in any good IC video.
Snake - Yeah, it might be a shock to see him this low. He just looks -slow- to me. His attacks don't seem to come off quickly. This may be a poor conclusion off small amounts of video, but it's the one I made. One thing that really interests me about Snake is that strangle move. I really want to see that in action. Does it stun for a long time? Is it hard to pull off? Is it broken? Can it be broken? If that can consistently be done and well, Snake may quickly rise to top tier. He's kind of a difficult char to pin for me, since he's so different. Weapon oriented, stealth oriented, etc. Can't wait to play as him.
Low
Donkey Kong - He's probably the best heavy character if Ike ends up fluking out majorly (which is definitely a high possibility). He's pretty quick, has some very good moves, and can own in the right hands. He is another character, like Mario, that really doesn't excel in anything, but isn't horrible, either.
Pikachu - Pikachu is an example of a character with speed that doesn't do too well. Pika is very strong for a little rat, very quick, and has awesome recovery. Migh major concern with the guy is his lack of range and consistent ko attacks. His smashes are probably the best combined smashes in the game, but he can't use them often because they require he's close, where he gets beat down. Pika is a nice character though. I wish he was better.
Yoshi - Yoshi had one major flaw in melee: his up b gave him no distance. Now that it does in Brawl, Yoshi's double jump cancelling, smashes, yumalicious eggs, and just overall comboability should make him a decent character, but nothing special.
Diddy Kong - "Unfortunately, screenshots fail to truly capture the way he moves."
That line confuses me. Is he quick? Is he.. low to the ground? I want to know, man! Anyway, I see Diddy as a very quick, pikachu esque character. He's about the same size, probably quick, and probably as similar tilts and the like. His up b looks really crappy, in my opinion. If you can't reliably actually make it back, you may as well never try. :( Peanuts also seem like they would probably be less beneficial than a traditional projectile because of explosions and edible peanuts. I can't wait til someone perfects the kamikaze popgun explosion, though. x)
Bottom
Pokemon Trainer - Though it seems like a fetching concept at the start, I can't see many, if any practical uses for pokemon switching. Unlike in pokemon, there's no real tactical advantage in changing pokemon because you're fighting the -same opponent-. In which case it may become more of a "play one character primarily, and switch when that one's about to die". The mobility of a pokemon like ivysaur must be limited, while squirtle probably isn't captain power himself, while I doubt Charizard's all so great in everything, either. Since every pokemon will likely have a flaw so all three "get used", I see PT's usability severely hampered.
Zelda - She is just Zelda. Slow and unable to deal large amounts of damage, Zelda is limited to the number of toes you get in. I really hope Sakurai makes her better, but I don't see it happening. :(
Bowser - Two lines convince me Bowser shouldn't be at the bottom like in melee. The first is, "The biggest and the heaviest of fighters, Bowser has a slightly different flavor this time around!". The second, "This time, there are several moves like this among the heavy characters, so watch out!", refers to invincibility midmove. The first seems to suggest Sakurai realizes Bowser really sucked, and wants to make such a "powerful" character better. I don't see his efforts going so far considering Bowser's slow, but it's worth a try. The second line makes me smile at the fact that it's nearly a guarantee Bowser won't be unable to fight because little, puny attacks keep flinching him midmove. If he can continue attacks now, he'll at least be on a somewhat even playing field with little tiny pikachu headbutts.
Lucas - Ness sucked. He wasn't powerful, had a crap recovery, slow moves that stunned him, poor projectiles, a horrible air game, and really crappy smashes. Lucas=Ness, effectively. Lucas, therefore, should suck. Sorry man. I'm hoping I'm wrong.
Kirby - Specials are really bad, throws don't do much, he's laggy, aerials have poor range+knockback, recovery -really- sucks for a character with multiple jumps. Sakurai went way too far in nerfing him from SSB, and I haven't seen evidence of change. Again, I'm hoping, considering the Kirby games are like the third most amazing platform series ever, that Kirby gets his act together.
Wario - He is fat, therefore likely heavy with a poor jump. His two moves revealed so far are the bike and the wario waft. The problem with the bike is
a.) it seems to be of no attacking use and
b.) if it is of attacking use, the opponent can use it too. It's like giving Marth's sword the ability to be knocked out of his hand so anyone can use it. It's pointless. Who cares if you can do a 180 turn on a bike? I want a practical move! The wario waft's major problem is you need to charge it. The imminent flaw in this is, if you're using it, as intended, for recovery, you can't get very far because you need to charge to get any vertical distance. By then, it's probably too late. Second, there's still no real attack purpose for this. What are you going to do? hope someone walks over you so you can crash into them? hope someone stands around so you can blast them? It has no practical attack usage either. And based on the other Wario moves we've seen, he seems to be a poor character. It's a shame, because he's Wario, man. Oh well. Bottom of bottom tier isn't so bad.
So yeah. That's my tier list prediction. it's probably way, way off. It doesn't account for likely characters or characters I'd really like to get in, such as Megaman, Ridley, Krystal, Falco, Olimar, Dedede, Nook, Stafy, Little Mac, Balloon Fighter, Cel-Shaded Link, Ganondorf, Captain Falcon, Jigglypuff, Luigi, Marth, Game and Watch, Ness, or Isaac. But it's decent, right? Feel free to pick it apart, because intelligent, critical speculation is fun. Yeah.