Where oh where to begin... I guess the start is as good as any place:
Back in the old arcade, 8-bit and 16-bit days, Double Dragon, Streets of Rage, Golden Axe Mortal Kombat and Street Fighter 2 (although I wasn't very good at the later two) were what occupied my time... well, any beat em up really.
Upon getting a PC in 1996, I enjoyed games such as Red Alert, Warcraft 2, Carmageddon, and the odd FPS (Terminator Future Shock and Skynet was probably one of the few FPS games I played properly).
Fast forward to my next set of PC gear, I had a new PC and purchased one too for my bro so we can play games on LAN together. Diablo 2, Unreal Tournament and Red Alert 2 reigned supreme on this gear.
Another few generation of video cards later, we were both sporting Geforce 3 Ti200s. UT, RA2 and D2:LoD ran better than ever but we also got into Serious Sam, Jedi Outcast, Freelancer, C&C Generals, Battle for Middle-Earth, and BF1942. I occasionally played UT2003 but that was more miss than hit but UT2004 was quite the comeback. Towards the end of this rig's life, I finally decided to visit C&C Tiberian Sun since I had never played that through.
Then came my last desktop with a 8800GT. All previous games ran better. I also caught up on NFS: Most Wanted (the first one) and my bro and I got into Serious Sam 2 and C&C3 (we love our co-op). Our PS3s more or less took over in 2009 but I did manage to sneak in reasonable bit of Red Alert 3, Torchlight, Starcraft 2, Mafia 2, and of course, Diablo 3.
Currently using my laptop until I get a new desktop.
What was my fav past game besides Diablo (I'm assuming any Diablo game)... I'd have to say that UT99 made the most impact. The last few patches negating the CD check meant that my bro and I could LAN on the one copy I had bought for him and the plethora of mods, models, maps, and mutators from the community kept the game fresh for years to come. There won't ever be a gaming experience like it IMHO.
What am I playing now? That web based C&C Tiberium Alliance game. I just love C&C as much as I love Diablo and I just wish they would bring out another C&C game set in the Tiberium universe. I guess I could always go play C&C3 again. That was quite fun.