The series has radically changed since it's days on the Genesis. Many fans of the original Sonic games don't like the recent ones in the same sense that a FFIII fan may not be too fond of FFX. Except the complaints about Sonic's decline are much, much less exaggerated. The addition of dialogue is what killed it if you ask me.

YouTube - Sonic Adventure 2: Battle: Hero Cutscenes (Part 3)

That video could be spoilery, I wouldn't know.


Anyway, I think the less well received games have a place, but personally I'm not too fond of them. My personal favorite is Sonic 2, but I don't habitually play that sort of game. It's purely nostalgia; it was my first video game.