Sonic is the coolest to me. Though when playing Sonic 3 & Knuckles, Knuckles to me is the best. Then Sonic, only because the game is longer with Sonic. I just like Knuckles power to Glid & climb.
Hmm...its not bad. BUT! IN my honest opinion the level design is terrible, its just a matter of luck before you eventually end up in some spikes. Also, consider making it in a lower resolution. Otherwise, the engine is pretty good
Its now taken me this long to get to Chemical Plant Act 1. And its an awful idea for a level. At least make some air bubbles or something for Sonic to breath, its virtually impossible to get to the end of the first long run of water without dying. Lower resolution too, to speed the game up!
Well, Sonic games are really well known for memorable moments, like running over the water in Hydro City in Sonic 3, or Knuckles vs. Mecha Sonic in Sonic and Knuckles. You have got to include that.