I have just been trying out some of the more recent roguelikes over at http://www.roguetemple.com, specifically Xenocide which has been a lot of fun, and Incursion which is too complicated.
IVAN is great fun, and quite good graphics for a roguelike too, without sacrificing gameplay. The limb / material / difficulty systems are quite phenomenal.
ADOM is good for a longer investment, it's more of a standard RPG rather than dive the dungeon.
Oh, wow, I didn't realize Incursion was ever released, I only saw a pre-pre-prerelease version a few years back and I thought it had stalled. (The "Westley Weimer" mentioned on the main screen is the programmer on Broken Hourglass.)
I find I'm just too familiar with ADOM to play anything else. Well, unless it's the rogueish Sword of Fargoal on the C64...
I'm a nethack junkie, my record is getting a samurai to the botthom level of gehenmon, unfortunatly at the time I had no idea that it was the bottom level, or what the vibrating square was for.... shame I lost the save file for it really.
I highly recommend Graphical Linley's Dungeon Crawl, though I would also encourage people to check out the various Roguelikes available on home consoles and handhelds like Shiren the Wanderer and many others.