You seem to like ARPGs as well, so I'm gonna toss in both.
Borderlands 2 (easily the better of both, but you could try Borderlands complete since it can be had for like 5 bucks too)
Torchlight 2 (Torchlight with mods is also good, just not as good)
Titan Quest* + Immortal Throne* expac (get these before there's a problem, THQ was the publisher)
Path of Exile* (online F2P in Open Beta now, pretty stable, no more character wipes, only cosmetic stuff and extra stash tabs for purchase, very good and if you turn off chat you'll only see some other players in the towns)
The Secret World* (this is a MMO, newly without any sub, like Guild Wars you only buy the box, cosmetic only stuff for purchase in the shop, massive amount of non-group content that is uniquely interesting, literally have never seen it in any other game).
Dungeons and Dragons Online (pretty self explanatory)
Fallout* and Fallout 2 (pretty much "duh" choices since you enjoyed Arcanum)
Fallout 3 and New Vegas* (different style and play style, same feel and theme)
Divine Divinity (I find it "meh" but a lot like it)
Gothic* (you really should play this)
Nox* (most people would call this an ARPG and most people would be wrong - it's also really good, I recommend the pet class)
* Must plays, if you're having trouble selecting, pick these