In the making of Torchlight, a lot of former Blizzard employees, previously working on Diablo, were involved. And I have to say, you'll definitely feel like you're in a Diablo game. It has the same addictive item-gathering gameplay, but with a few novelties and enhancements to bring it to today's standards. E.g. you have a fighting pet, which you can train and teach spells. You can also send it to sell your stuff, while you continue to raid the dungeons.
The best way to pass the time until Diablo III comes out.

Basically the same game as Fallout 3, but with a few enhancements and new elements, e.g. weapon mod kits, hardcore mode, and a better dialog menu for companions.
If you didn't like Fallout 3, you won't like New Vegas, but if you did, you'll like this game, too.
Also be sure to check out some mods at www.newvegasnexus.com