D1 to me felt like the more complete game, all of it's features are well implemented. Sure, fusion is a little overpowered, but its supposed to be a very powerful weapon. And in order to use it in multiplayer, you need a certain degree of mastery. I never reached it with fusion, but I was nasty with plasma in a way that I feel was close to top tier when I was at the top of my game (before the last time I quit the IDL).
D1 textures seem more like they belong there. A lot of D2's levels had a cartoon-ish feel to them because of the textures.
D1's robots also felt a lot nastier. Each one of them gives off a certain impression that D2's robots just dont. Most of the D2 bots in the first few levels feel like knock offs of D1 bots.
D1's weapons were also better balanced. Lasers, Spreadfire and Plasma were all on the same level, and Vulcan was hard as hell to use because it was continuous fire. Meanwhile the only D2 weapons that ever show up in a D2 one on one match are Guass and Mercury Missiles. Flash missiles are too hard to use (and I believe d2 3dfx nerfed their effect), smart mines are overpowered, guided missiles are useless, shakers are reserved specifically for shaker levels (one of the few d2 specific levels I like...I need to play hoard in UES sometime) because theyre so devastating. Megas also get left out, but in a Dogfight those are pretty easy to dodge too.
The other guns also suffer some problems. Omega was too framerate dependent at the time to be a fair gun, phoenix was too clumsy, and no one besides me seemed to like the Helix cannon. I thought the helix cannon was probably the most finished new primary in D2. Guass seemed overpowered because of its kick when it hit you, also its lower rate of fire made it slightly easier to use, so everyone used it. And then the nerfs that D1 weapons got in D2 are just infuriating. Spread got nerfed (I believe in addition to the slight damage hit, at max you could only do two bolts of damage), D1 super lasers do less damage than d1 level 4's (50 vs 52 iirc), and fusion was castrated. This lead to D2 dogfights consisting mostly of plasma vs guass, with the occasional laser user.
So in D1 matches you have Lasers, Vulcan, Spreadfire, Plasma, Fusion, Concs, Homers, Proxmines, and Smart Missiles.
And in D2 matches you have Lasers, Guass, Vulcan, Spreadfire, Plasma, Concs, Homers, Proxmines, Smarts, and Mercs.
Personally I would have loved it if a few of the popular D2 levels included everything but the Earthshaker. Phoenix and Helix are both interesting guns that make for amusing dogfights.
I guess what frustrates me the most about D2 multiplayer is that even the people who played D2 over D1 didnt use a lot of the D2 features and weapons. They all tried to make it like D1 with afterburners and an improved vulcan cannon. What was the point?
Back to single player...
The secret levels in D1 also seem better. Theyre insanely hard without any gimmicks. The D2 secret levels often felt akward.
Also, forcefields and shootable switches were hard to figure out a lot at times in D2. Hit a switch and nothing apparent happens...you may have to go through the whole level and even then sometimes you wont know what that switch did. Some kind of indicator, like a blinking cube on the automap (for what good it does, see below) would help to figure out what the things do.
The level designs in D2 are non-intuitive as well. The very fact that they had to add a guidebot so you'd know where to go is testament to that fact. One of my favorite things to do when I play cheat mode for kicks its to just nuke that jerk as soon as I blow open his cage.
One aspect that sucks in both games is the automap. The thing becomes unuseable in any level of a decent size. The D3 automap is a little better, but not by much. I hope one day we figure out a good 3-d automap some day, or just abandon it like pretty much every other first person game newer than doom has done.
D1's breifings add a lot of atmosphere that D2's lack. In D1 you get to hear about the level before you enter it, along with robot intel. In D2 its just robot intel and some cutscenes between palette- er- level sets.
And as fun as the Earthshaker is in multiplayer, that level 24 boss seems just excessively overpowered, even at lower skill levels. Oh, and dont get me started on homing flash missiles... And whats the point of those diamond claws producing smart globules if you hit them with anything but guass? Did they put that in so the robot could fight back when youve got it held stunned with continuous fire?
Okay, rant over. D2 is still a very good game... in single player. D1 is very good in both. D2 could be good if less of the weapons were declared \"lame\" by the community.