Worst: Sonic 4 episode 1 Mobile Version
Sonic Colors Wii Version
Sonic 3d blast: Flicky's Island Genesis version.
Why?
Sonic 4 episode 1 brought nothing new to the table, the controls were a mess, Sonic pretty much walked through the game, (literally,)
The character writing in Colors was grating, Sonic never stopped talking. Gameplay was alright but was nothing that stood out for me.
Sonic 3d blast's Isometric view made it difficult to see where you were actually going, never finished the second act. (maybe it's my fault for just being bad at it.
Best: Sonic Adventure 2
Sonic 3
Sonic Generations
Sonic adventure 2 has excellent writing (especially for Shadow,) a thrilling plot, and diverse gameplay styles that becomes more enjoyable as you replay it.
Sonic 3 tells an excellent story even without voice actors and makes you feel part of the adventure the deeper you go.
Sonic Generations combines 3d and 2d elements with excellent level design, although the story takes a backseat, you get to revisit iconic places from past games, remixed music sounds awesome, and it is overall a great experience.