Here we go....
Ok, before I say anything else, I want to say that the amount of work you put into this is incredible, and I'm a big fan of this for what it is.
Now that I've got that out of the way, I can get down to the nitty-gritty, a few things that could make this game even better (perhaps in a v2 release?).
As this is a recreation of an existing arcade game (which I have no objection to - good work!), certain subtle differences in the gameplay become much more glaring. For example, sonic's response to a left/right movement are far too sluggish, meaning it's even tougher to put the breaks on than in the original. Secondly, when sonic jumps onto platforms, just landing on the edge, he falls off rather (often to death) than catching on - this severely damages the smooth speed of the sonic game.
But other than that, the game is a pretty damn sentimental experience. Those were the days, when sonic wasn't cursed with an annoying Californian accent and a retinue of over-the-top hangers-on. I mean, Amie? WTF???