I was blessed to grow up with Doom, and especially Doom 2. My dad and I had subscriptions to DWANGO (Austin, specifically, but if I wanted to rack up long distance fees, I would dial into Houston), and then my Uncle opened up his own BBS (Bigtoe BBS). I can't remember the protocol that was used, but it later allowed matchmaking with Warcraft 2 and Duke Nukem 3D. I remember Quake 1 making our dialup connections cry. Quake 2 birthed the built-in internet support, but no matchmaking and required servers. But I digress... Doom 3 was a disappointment for me, because it lacked co-op, it lacked speed, lacked monster density, and the environment didn't "feel" like Doom. Not just the coloring, but the whole thing. The music, the sounds, too many boring, claustrophobic hallways. Switching between flashlight and gun was pretty stupid, but later fixed, obviously. There were no huge sprawling outdoor areas. It wasn't macabre, as someone also mentioned. It had all of Carmack's wonderful engine, but none of the original team's design aspects that made the original Wolfenstein and Doom games great. Level designs weren't very involved in Doom 3, and it really wasn't a challenge. Difficulty levels with a variable number of monsters is also something Doom did that is done very, very infrequently. Back to co-op, that's the reason and only way I'll play Halo.
Also as Croetec pointed out, the guy playing in those demo reels sucks at FPS.
Things I remember about DWANGO... my dad played primarily with an old joystick, and I was a keyboard cowboy. Once we logged in and got our asses kicked, we were learning mouse the very next day. DWANGO 5 Map 1 was the definitive map, but I think Map 4 or map 8, and the other DWANGO wads (1-4) were used regularly. Most folks shunned DWANGO6 because it was made by a different author, but it still had a good version of map 1. Having a faster computer meant your shots were prioritized, and folks with Pentium 75+ were notably more "accurate" than DX2 66's or below. Felt like hot shit when everyone started getting 120 and 150 MHz procs. And when having a SB16+ actually made the game sound better.
DOS command line launching, and the launcher application for local games. Shit used to be such a challenge to find matches.