warning: tl;dr. I tend to do that.
I played the shit out of Sonic 2 back in the day--it came with my Genesis--but now when I reach for a 2D Sonic to play I go for S3&K. When I first played it I thought its levels were way too long, especially Carnival Night 2... but paradoxically, now when I play Sonic 1 or 2 I find their levels too short. S3&K is such a masterpiece of level design (or at least it was until zip glitches broke it beyond repair), doing so much with limited memory and processing power, I think it's the best 2D platformer ever made, rivaled only by Super Mario Bros. 3. I haven't tried to TA it because every time I start to play it I try reasonably hard to go fast for the first few levels, then invariably find myself slowing down to just enjoy playing it. I thought the decision to use new BGM with every single stage was bizarre at first--when I heard the act 2 music in Carnival Night and Ice Cap, for example, I thought my Genesis was malfunctioning and not playing it properly--but now I love it. I would maybe give it a 9.9 and not a 10, though, because as someone who remembers playing it before the Internet, I cannot banish my memories of initial frustration brought about by that barrel. And also the vertical wrap oversight glitch in S3 alone that inevitably kills you in Ice Cap 1 as Tails.
I do love Sonic 2, a lot, but just not quite as much. It's a very solid and balanced game--nothing really jumps out at you, but nothing to bother you either--except Chemical Plant 2. I literally had NIGHTMARES.
The first Sonic game would probably not rate as high for me, because I literally love half of it and hate the other half--I love Green Hill, Spring Yard and Star Light and hate Marble, Labyrinth and Scrap Brain. I understand what they were trying to do--balance speed stages with platforming and puzzles--but to me they get away from what's become known as Sonic-style gameplay too much in them. Labyrinth and Scrap Brain have some horrendously cheap aspects of their level design and Marble is often very slow because of autoscrolling lava blocks and what not. Sonic 2 and 3 balanced this much better. Also the final boss was pretty lame.
As far as 3D Sonics go, I think it goes without saying I love Sonic Adventure 2. The soundtrack is incredible, the multiple missions give it a lot of replay value, and of the 3D games I've played it executes its level design the best. I understand people disliking the hunting stages, and the randomness is undoubtedly frustrating if you're trying to speedrun (ESPECIALLY Security Hall), but for casual play I generally enjoy them as a change of pace... Meteor Herd and Pumpkin Hill are my #2 and 3 most favorite stages in the game, due most likely to becoming intimately familiar with them on my first playthrough (I remember Pumpkin Hill taking over 18 minutes to beat, and Meteor Herd nearly 15 minutes.) Plus, there are some really, really cool and entertaining glitches (see: any of SadisticMystic or son1cgu1tar's videos). The only thing that bothers me is the requirement of raising a Chao to unlock everything; I have never even hatched one and that's why I have no Green Hill stats.
It's hard for me to formulate an opinion on Sonic Adventure because it literally makes me sick--if I play for more than 30 minutes at a time I get motion sickness so bad I've puked from it. Its level design to me is much more ambitious than SA2's--compare the down-the-building run in Speed Highway to City Escape's, it's not even close; or the snowboarding section of Icecap vs. City Escape/Metal Harbor, where it's practically an afterthought--but not executed as well. Casinopolis is flat out boring if played the "proper" way--you practically have to try to fail at the games to get any actual gameplay in the stage--and Lost World can get extremely frustrating, especially the first part with the stone snake in the water. The Adventure Fields were either awesome (see: Egg Carrier) or way too big and sparse (see: Mystic Ruins). I do like that it incorporated a lot of classic elements from the Genesis games like Sky Chase (doing it twice was a bit much, though). And some of the levels like Windy Valley and Red Mountain were very creatively designed.
Sonic Heroes could have been awesome if they had just put more effort into making it play properly. The level design was generally solid, music was very good if sometimes repetitive, none of the enemies or bosses were particularly cheap, and the team dynamic was something I'd wanted in the game for a long time--but it is So. Damn. Glitchy. You should not randomly fall through solid floors and die (see: Bullet Station), and when the game tells you to use your Speed character and light dash rings, those rings should get you where you want to go, not leave you completely screwed (see: Power Plant, Dark, end of the stage). The game relies far too much on bottomless pits for difficulty, which becomes a serious problem when combined with its glitchy engine. There are also cheap camera tricks resulting in fake difficulty (the gator chase at the end of Lost Jungle). It's too bad because the game actually feels a lot more like an older Sonic game than either of the Adventure titles did due to the removal of upgrades, random hunting levels (Chaotix levels have consistent locations), chao, etc.--the game design is much more streamlined. Hang Castle, Mystic Mansion and Egg Fleet are my favorite stages.
Like Sonic Adventure, Sonic 3D Blast causes me to get motion sickness. It took me three days to finish the first time despite only dying three times due to constantly having to stop playing and get my stomach settled--a save feature would have been nice to save wear and tear on my Saturn. (I shudder to think what Sonic X-Treme would have done to my poor stomach.) A few stages like Gene Gadget and Volcano Valley are somewhat fun, but the isometric POV can be pretty punishing when you have to make precision movements and jumps to avoid traps--Spring Stadium is a clusterfuck of them. At least there are no bottomless pits or water, and it had a pretty impressive and challenging final boss.
Sonic Spinball is what I would call a rental game--it's fun and novel at first, and has some good music, but the novelty wears off quick because it is WAY too short. If you paid for the game when it came out (or your parents did, as in my case), you (or they) probably felt ripped off.
I have Sonic CD and Shadow, but I haven't played either--CD because I am a coward and afraid of getting bad ends, and therefore intimidated by the time travel mechanics, and Shadow because I am afraid of the inevitable assault on my ears by the horrid 4kids voice actors. As you can imagine I haven't played any of the newer games--I don't own a current generation console and my computer is a five year old laptop. I also haven't really played any handheld Sonics because I'm admittedly prejudiced against small screens--I want to play on a big screen. I guess I don't have any excuse for not playing the Advance games, though, since I do have a Game Boy Player for my Gamecube.
