lol @ this depression.
I would totally give advice... if I knew what the **** I was doing with Sonic. Or anything in this game for that matter.
If you did hit a plateau, it always takes some kind of advice to get over it. If you really did post replays and people really ignored them on purpose (because, you know, the Internet is such a crazy place that has a wealth of info being poured into as you read this), then maybe you need more persistence in getting the advice you seek, or maybe you should just PM someone to actually help you out.
I could be wrong, but I feel like this game is more matchup knowledge and good reads while almost totally lacking any real necessity in the execution department (see untrained MK's beating up on fully rehearsed execution based characters and Falco's chain grab + laser camping dominating half the other characters). Obviously there are exceptions (I still haven't learned IC's CGs because they really aren't "learn in 3 minutes" techniques and I couldn't give a **** to spend 12-27 extra minutes to learn it), and Sonic seems to be one of those exceptions (but doesn't X use Sonic '08?)
So the question is what exactly do you feel your problem is? Do you lack matchup knowledge? Do you have the theory of matchup knowledge down but the theory isn't translating too well in the actual match because of other **** that comes up (like people countering the strats that Sonic would need to use to win)? Are you simply just not as good as the people you play and maybe you just need to level up gradually starting with players that aren't as good because it seems like all you ever play are people that are better than you? Maybe you just need to play the computer a few games (I don't give a **** what anyone says, you CAN learn things from playing the computer... but a lot of the times, it's simple, minor bull**** that most people don't know but the game knows... like, Vega's claw, for example, has plenty of range and speed, but no priority at all in most games, and gets stuffed by 90% of every attack in the history of Street Fighter).
Maybe the advice that you need has nothing to do with Sonic. Or any one character, for that matter. A lot of the time when I get over plateaus in other games, it's due to either learning something about the game itself, learning something from another character, or learning something about the psychology of fighting games in general.
Like, the most recent thing I "learned" about top player game play is that the difference between a top player and a intermediate player is how they see the game. You'll see top players do **** that theoretically doesn't make sense (see Daigo doing a Dragon Punch simply because the command exists) and when other players try to emulate it, they get smashed (see random player whiff random Dragon Punch and eat an Ultra upon landing). It's because with intermediate players, they see and play the game as a science, but as a top player, they see and play the game as an art.
When I read this, my Chun Li in Super Turbo exploded off whatever plateau I was at. I don't just play matchups anymore, I do whatever the **** I want within the context of the matchup (assuming I know the matchup... I still don't really know how to fight T.Hawk, Honda, and Bison, even though she supposedly wins those relatively easily.) I can hang with top players much better, even if I'm still losing the overall sets, and I'm having waaaay more fun with the game, even against Hawk, Honda, and Bison, the matchups I don't know.
And at the end of the day, this is definitely something that Sirlin didn't teach: having fun within the context of playing to win. You can have fun while not playing to win, and you can play to win, but not have fun doing it. I think that when you are "having fun" "playing to win," then you can explode off of plateaus that you may be on. And then your mind might be able to pick up **** that you may or may not have been doing wrong. I would like to believe that minds learn the most when the situation is fun (second only to when in danger).
Hopefully, if you have any psychological or philosophical barriers in playing this game (or any competitive game that you might be involved in playing at a relatively high level (i.e. able to make all your friends hate playing the game with you to the point you're pretty much Attitude Era Triple H) (who, for the uninformed or amnesiac, was a bad-*** WWF heel during the height of wrestling in the 90s that everyone pretty much wanted to see lose because he was so good at being bad), then that might have put some cracks in the wall.
tl;dr version: I like to write. Read the ****ing wall of text.
Edit:
http://www.youtube.com/watch?v=rPygYyoEaCI
Loveyoulongtime Kyle.