On TL2 vs. D3...
I find Diablo 3 so boring that it's criminal. I recently played again a bit as a Barbarian (originally was a Monk, but I realized I was only having fun with the game because I was talking shit to my friend while we played), and was really only mildly diverted. As in, I played for a while, asked myself if I was having fun, wasn't certain, so I kept playing to continue considering the quandary. Finally, I went "Oh! I get it. I'm just slightly interested. Like reading a magazine in a reception area." I find the graphics boring (I love the general aesthetic, I think they just managed to make it look boring as opposed to D2, which really managed to capture my imagination in some areas), the music tasteless (like "Gee, this plain oatmeal sure does lack flavor!"), and the voice acting either terribly bland or banal and insipid, which are adjectives I'd reserve only for the story (a story which I Found vaguely interesting in D1 and D2!).
TL2 is more interesting to lack at, the battles are more frenetic and the skill synergies are more interesting. The classes have more personality. The story is completely forgettable, but I can't think of a game like one of these that kept me engaged and curious other than like Baldur's Gate: Dark Alliance 2, and I think that was because there were class quests.
All that said, I'd be willing to play D3 with a group of people who were similarly interested. I'd just say that when I'm alone, I don't find it barely engaging. Playing with people would probably make it a little more fun. TL2 is something I can enjoy alone, though, and friends just make it much better.
All I can really say about BL2 is that I found it a complete improvement in every way except for Zer0 not being as fun of a melee character as Brick, and that issue has been mightily resolved with Krieg. I still find that 98% of the jokes fall flatter than a pancake throwing itself from a high-rise building after being dumped by it's fiancee', but I generally don't care. I just tune most of it out unless something sounds a little promising and chop up baddies.
I haven't had a loot issue in any of these games. Course, I have yet to do the intense loot hunt in D3 (which people claim has been hamstrung by Blizzard in an effort to go after that RMAH money), but I don't much care and if I wanna play the game without it (and presumably with adjusted loot rates), I'll get it on console. Hell, I might anyways, because click to move sometimes aggravates my wrists.