I beat this game this morning. The ending is retarded. Seriously retarded. WHEE YOU BEAT LORD IX AND WINNED TEH GAEM EXCEPT ACTUALLY NOT REALLY BECAUSE AFTER YOU BARELY GET BACK TO YOUR OWN WORLD IT TURNS OUT DR. ROBOTNIK HAS TAKEN OVER THE WORLD IN A COMPLETELY UNSURPRISING AND UNIMAGINATIVE PLOT TWIST. Oh, and then it's a cliffhanger ending. WTF Bioware.
That said, I still enjoyed the game, all the way up to the end. So that says something, I suppose.