Yeah, I have to second that you give After the Sequel a go. It's better than Before the Sequel, and much more like classic Sonic than Chrono Adventure. The soundtrack rocks as well, and some of the level themes are pretty original. You just have to get used to Sonic World's physics and a few less-than-professional graphics. As for Nexus, I'd love to see that come back in some form. I used to check on that project's blog every day back in '08 hoping for a new demo. It always seemed so... solid compared to other fangames of the time.