Musashi1596: I can't even remember if I bought Ultima VIII on here or not, this is how badly I'm falling behind with my gaming... Still haven't played Divine Divinity either.
Ultima VIII seems kind of crappy to be honest. IV through to VIII Part 2 seem like the ones to play. I've only played IV extensively so far, but I wholeheartedly recommend it.
I think if you're into Arcanum you would really like Divine Divinity. It's an action-RPG, but with as much in common with traditional RPGs like Ultima and Arcanum as it does with Diablo. Despite its tactical nature, I actually think that Icewind Dale is closer in spirit to Diablo than Divine Divinity is.
If you're not too picky about having an overhead view, the Might and Magic series is also worth checking out. It's the same style of game, except in first person. Might and Magic VI in particular is pretty crazy because it has a huge, detailed open world combined with a huge dungeon crawling component to it as well. It's pretty unique, probably my favourite RPG.
I haven't played Neverwinter Nights 2 yet, so I can't comment on that. But I have played Dragon Age: Origins, and I think it counts as an old school, hardcore CRPG with an overhead view, though there were some major problems with the game. Ditto for Drakensang: The Dark Eye. I haven't tried the newer Drakensang: River of Time yet, though by all reports it's a much better game than the first. But if you hate Neverwinter Nights 2, you might not like these games.