You're pretty much limited to prjects that use ProSonic, E02, or some other replica engine that I'm not aware of...
Uhh, dude.
Retro Sonic. While it's gone through many iterations, the engine is now very accurate, and it feels like a professionally done Sonic game. And PC game, too. If you want to have a taste of its quality, just try the Sonic Nexus Labor Day 2008 demo. Nice physics, special effects, and provides an all-around great experience.
Regarding Ultimate Flash Sonic, I tried it for twenty seconds, and then promptly closed it down. I don't understand how anyone can believe that Flash is an adequate platform for game development. It's incapable of maintaining a proper 60 FPS, playing sound without lag, or drawing raster images properly and efficiently (they're forced into vector space which means slowness and ugly, inexact pixel transformations). It also can't provide true fullscreen (as in, resolution change), nor does it allow hardware accelerated graphics. It has no built-in facility for frameskip, so when Flash games slow down (not an uncommon occurrence), playability is lost.
On a similar note, I wish Stealth would stop trying to advertise his E02 engine as a general purpose game platform. These days, most people want something above 320x240, 256 colors, and low-quality WAV sounds. Unfortunately, you can't get that. Instead, you have an unreadable, proprietary scripting language, an editor with extremely small screen space, and a filesystem littered with .def and .pcx files, and 8khz monaural WAV files (yes, this is actually used for the music). Stealth tried to improve the awful music quality by adding support for different music files, but instead of doing the sensible thing and adding support for compressed audio (like what Taxman did with Retro Sonic), he added homegrown XM music playback.
Anyone who has an interest in module music will want something with proven accuracy. A homegrown module system doesn't have that. So who exactly is Stealth's target audience? Apparently nobody. I predict that E02 will fall flat because of this very reason. No developer in their right mind would ever want to use such an outdated and limiting system.
Wanted to get that out, is all.