Long post ahead afgak...
I guess some voting would help out here on what we should do. I think finding out what we want is a good place to start.
-Should we collect all emeralds?
-Which games would you like to be feature in the playthough and which are "excessive baggage"?
-What about games with the same title but are featured in different platforms (Sonic 1 Genesis/Game Gear versions)?
-What about the final story/boss/levels?
-Any game should be played as Sonic/SS unless a variation of playstyle and layouts are available.
-If another character can do a certain stage faster than Sonic, should they be switched for the time being?
-What about Tails? Should a second player be controlled? It'll help in Hydrocity 1 in the beginning, bosses, and a few other areas.
So in order of mainstream games:
Classic-
Sonic 1, Sonic CD, (SegaSonic Arcade?), Sonic 2 (with Tails?) S3&K, (Knuckles' Chaotix?) Sonic 3dBlast, (Sonic the Fighters?), and then Sonic R(?)
-Sonic CD can be a bit problematic whether we should go to the past and future stages, US vs EU/JP soundtrack, and Time Stones collection.
-For Sonic 3, two playthroughs; one for Sonic's story, and then another for Knuckles'.
-Sonic R=should we do this? If so what about unlocking characters and difficulty settings?
Modern-
(Sonic Pocket Adventure?), Sonic Adventue (DX?), (Sonic Shuffle?), Sonic Adventue 2 (Battle?), Sonic Advance, Sonic Advance 2, Sonic Heroes, Shadow the Hedgehog, Sonic Rush, Sonic Battle, Sonic Advance 3, (Sonic Riders?).
-Should we playthrough all the other three teams in Sonic Heroes?
-Playing through Rush from start to finish with both characters can be finished quickly; whether we should get to the final boss or not.
-For Shadow, I think the best tactic would be to do each stage once. Getting a file that has already completed the final boss will take out repetition of levels. We could just take different routes until each stage is eventually played, then move onto the final story. The other tactic would be to do "everything" and start from a non-save. This can take quite a few hours to do, so I really would suggest to avoid it. Most of the level objectives are monotonous work and time consuming anyway; it'll get boring quickly.
-For Advance 2, I guess we could do the same thing and just do a play though from start to finish on an all character save file and play as Sonic and get all emeralds, then move on to True Area 53. Another idea would be to show the storylines of unlocking the characters, stop recoding and do Tails, Knuckles, and Cream fully while recording another game; and then move onto True Area 53.
-Sonic Advance 3 has different team work aspects and I think that character switching should be done every so often when feasible.
Current-
Sonic '06 D:, (Rivals?), Sonic and the Secret Rings, Sonic Rush Adventure, Sonic Riders 2: Shooting Star Story, (Rivals 2?), Unleashed, (Dark Brotherhood?), (Black Night?) D:
I'm not up to speed with most of these games. So I wouldn't know what not to do. I guess just play through Story mode and finish should be the easiest feat.
I've omitted all of the Game Gear and puzzle games and gave a question mark to those weather we should do or not as optional. We also have crossovers (Christmas NiGHTS, Superstar Tennis and Mario-Olympics) which should be put on a league of their own. I say that all of those listed up first up here should be done first. If time persists, we can go back to do the others. Doing the final bosses and collecting the emeralds aren't that hard, to do.
Edit: Cleared up a few things and forgot a few games.