I think you’re being too harsh. sure, games like ‘sonic unleashed’ and ‘the black knight’ looked too gimmicky (although I never actually played them so they could be quite good??) but people just jump on the sonic hateing bandwagon these days. ‘Sonic the Headgehog’ on xbox 360 (I think it was on ps3 as well) I though was really good. I like a good storyline in a game these days (although sonic 4 fits in with the older ones so is and exception) and the whole story of how the future was a hellish waste and silver is tricked and the sungod being contained and all that really made an epic storyline. And the gameplay was equal to that of the ‘sonic adventures’ which were brillient and also had (especially 2) good storylines. I only just bought ‘sonic colours’ today and all I can say so far is that even though the comedy aspect to all the cutscenes seems a little out of place and unneeded, the gameplay is solid and the classic mario style ‘unlock and return’ thing they have (similar to hitting ‘the red swith’ to make ‘red blocks’ appear etc) with the wisps is a very good idea to keep people moving back and forth through the levels.
I think that to keep going they should continue with more episodes of sonic 4 and every now and then bring out a new big sonic game with and epic plot. The only problem I can see is they brought too many games out too fast and had to think of a way to make them all different.