I mostly agree with lange, just because most of his opinions happen to be mine as well. Serephim definitely made some good points, and I can see why he chooses them. There's a few I actually share with him, such as his points about modern sonic fangames, and nostalgia.
There's one I'm in the middle of though...
What classifies a sonic fangame as a sonic fangame.
I believe that there is a certain level of criteria that needs to be met for it to be a sonic fangame, But I'm not too sure how to explain it well... I'll do the best I can.
Look at sonic BTS(or ATS). Honestly, they're not a lot like the genesis games. The physics are wrong, the sounds are a mix of sonic CD and the genesis titles, the music isn't retro. One could argue that the level design isn't the best sometimes. (just look at the ATS argument thread, ugh.) Really, the only thing that is keeping this like a genesis game is the graphics, the story, and the way the levels are structured. But...
You can feel that Lake's heart and soul was poured into this thing. You can feel he wanted to do this out of love for the franchise. He didn't do it for fame, or attention, and you can really feel it through the quality, and the way the fangame was built.
THAT is what defines it as a fangame. I don't care how crappy the game is, if you can feel that the developer really put some love and effort into it, THAT'S what makes it a fangame. Most of the time, it's pretty easy to tell.
This is just how I feel. If you think I'm wrong, please tell me, I would love to hear anyone else's side of the story.