[guard-of-terra]

Seeing as comments turning into a list of roguelikes:

ADOM is one of the best roguelikes. It's closed source but very deep and high quality. http://adom.de/

POWDER is a little graphical roguelike targetted at portable game consoles and PDAs. But you can play it from PC. It's reasonably quick and have a very fun and orthogonal skill/spell/item system. http://www.zincland.com/powder/index.php?pagename=release

[JoachimSchipper]

TOME (http://www.te4.org) is ADOM-ish (reputedly, haven't seriously played ADOM) and pretty fun. I found the level generation a bit repetitive, though.

[guard-of-terra]

I thought TOME is Angband-ish, isn't it? It's a very different branch of roguelikes.