This has to be, hands down, my favourite Sonic game!
I love the concept of creating your own character. It is slightly limiting, but that's fine. The controls are east to learn and are friendly to newer players. While some of the level are easy, I found a lot of the later levels quite challenging. The game has an interesting storyline and an intriging villian. Honestly I don't understand why this game gets so much critisism that it doesn't deserve.
Honestly I just wish that the game was longer.