Sonic Rush finally brought Sonic back to relevance with a fast-paced side-scroller, just the right environment for the blue hedgehog. Of course, this didn't stop series creators from needlessly introducing yet another character, Blaze the Cat, into the series, but who cares? They managed to somehow not mess up incorporating 3D elements (the boss battles) into a Sonic game, so that's an achievement in and of itself.
FUN FACT: The game is actually broken up into storylines for both Sonic and Blaze. If all of the emeralds in both are collected, a final story path is unlocked.