Titan Quest is pretty good, I'm playing that right now. Immortal Throne crashes on me every time I try to play it within a half hour or so, but TQ will run all day long, so I don't know what the deal with that is. Game itself isn't very well optimized though, needs a pretty beefy system to run well.
Dungeon Siege 2 is fun as well, I haven't played the expansion yet though, just ordered it a few days ago.
Dungeon Runners is a free online only game, worth the download IMO.
I've seen a game called Fate that looks somewhat interesting, never tried it myself though since it lacks any sort of multiplayer, but if you don't mind single player adventures it might be worthwhile.
Don't bother with Loki, it's putrid crap. I didn't like Hellgate either, it's definitely not the same vein as D2/Dungeon Siege despite what people say. I've still yet to play a dungeon crawler that even came close to touching Diablo 2 LOD though.