D2: Supers, Gauss, Helix(Oh, the sweet, sweet DPS; why couldn't we have kept this instead of Napalm/Microwave?), situational Fusion.
IMO, Plasma wastes energy compared to Supers, and up close where the damage rate could really matter, I'd rather cut loose with Helix. Now and then, maybe I'll use the Omega on the Thief out of boredom/annoyance.
D3: Supers, Vauss, Plasma(energy efficient spam/for stationary targets), Mass Driver, Napalm for random fun/Sickles, EMD for occasional Orbot, occasional Fusion.
While I do like D3's mission-objective variety(and not wasting several minutes killing off the Thief at the beginning of most levels), I think I like slower-speed D2 combat better. On any difficulty above Rookie, there really is no such thing as long/mid range combat in D3, unless you're using Vauss/MD(or wasting energy on EMD). With the exception of Tubbs and Sparky, even the weakest bots almost effortlessly dodge most guns unless you're practically ramming the barrel down their(proverbial) throats.
Also, I kinda like how D2's bots don't automatically come running when they hear you shooting. While it means they don't gang up on you as much, I think individual D1/D2 bots are generally more capable of causing real "oh crap" moments whenever you stumble upon them(apart from the super-Stingers/Tailbots and 'Blackjack' MD troopers EDIT: And the Napalm Gyro), and you can't as easily 'drag' them away to a more convenient spot to finish them off.
OTOH, D3 does have some more fun/creative missiles(Frags, Impact Mortars), and the Vauss was a lot more balanced(and arguably cooler-sounding) than the Gauss.