If you like Nethack at all, though it's been a few years since I've played them, I highly recommend Angband (
http://www.thangorodrim.net/, somewhat outdated website, but I'm not sure what the current one is) and its variants. ToME (
http://t-o-m-e.net/main.php?tome_current=0) is one I know of that's in active development these days.