List of 22 hacks:
http://www.romhacking.net/?page=hacks&game=714
I did a repro of Return to dinosaur island. Very good stuff, a bit on the easy side (no more than the original) but still very professional.
I also did a repro of The Second Reality Project 1 and it was very enjoyable as well. The main problem is the last stage, I can't beat it. I've thrown hundred of hours on it, it's not cheap hard, but it's definitely too long (we talking more than 10 minutes IIRC) so I always die at some point. Very frustrating :P but the rest of the game is top notch.