TL1 had some great potential. Unfortunately the devs (and I quote) "ran out of money." Now with TL2 around the corner, I think the ARPG genre has some needed new blood.
I think Diablo is on the right track for skill systems. Once I've settled into some nice gear, most of my time is going to be spent fiddling with different skills. Playing the TL2 beta, I didn't get this. I like to play with my skills and make tweaks, and rerolling from scratch is a bit too steep of a price to pay. But I guess that's one of the things mods are for.
I love playing D3, and after they iron out the kinks, the long game looks to be amazing (and pvp, but that's tbd :P). But moment-to-moment combat of Torchlight gripped me like no game has since TWEWY or Chrono Trigger or Portal or HL2.
Diablo 3 - Able to change on the fly, runes change skills dramatically, no unique snowflakes.
Torchlight 2 - Traditional D2 system, expensive/impossible to change, much more customization.
I disagree. The customization of D3 (especially when pushing into under-geared content) is, well, reliant on gear. The skill/run system has superior customization than skill-tree esque systems like in Torchlight, even if by sheer numbers alone. However, I think the customization in Torchlight is enough
that it won't matter. The combat in TL is what pulls me to that game, not the experimentation.