I dont think that Sonic has anything to prove. Sonic Team has made some steller games IMO. This is just adding to his popularity. You cant deny that Sonic has a pretty big fanbase, (which, I am a member of, sadly)and it hasnever been bigger.
In all honesty, the Secret Rings had mixed reviews, and Sonic nextgen was given a bad rating, but from fans, I havnt heard a bad word yet, and thats where it matters. Sonic has had some flops, but that shouldnt make people forget what kind of games he can make. Look, you cant deny that it made the day of millions to see Sonic announced in SSBB. You wanna know why? Hes a giant in gaming industry, and you should know it isnt for no reason. There are many other gaming franchises that outsell Sonic, but the 9th spot over so many is pretty good.
Sonic is doing fine for now, and TBH I think SSBB just got his weight in gold by adding Sonic. Just from hin being popular.
Good luck, Sonic Team.