I want to preface this by saying I can understand how D3's gameplay isn't for everyone. I know from experience that not everyone likes dark maps, for instance - I however, do. ( I doubt anyone here ever played it, but cs_spookhouse is probably one of the darkest map for CS made - and that was all my fault

).
Also, some of the fun is pure nostalgia. Most FPS games don't even bother to knock off id correctly - but here are all the old tricks back in action and some are fun as hell.
Yes, some have also just gotten annoying. Monster closets should be banned from level design, end of story. They're silly, they don't make sense, and they make me remember that it's a game, not an experience.
But man, some of these comments just sound wacky to me. Somewhere between the Half-Life fanboys and the people who apparently expected Carmack to deliver god-on-a-stick, gamer opinions often just seem to me.
Dynamic Gameplay? Meh, it's -how- you play it I think. Did you try not just using the stand-and-deliver approach? Maybe toss a grenade into a room, stir things up, lead them back to those flammable tanks?
Could it be more dynamic? Sure. A better inventory would help - trip mines, prox grenades, etc. I'll agree it's core is still just run and gun but there is more to it around the edges if you let it.
Anyone complaining about this lighting system needs to get their head checked. Jesus, some people are never happy. And the physics? OK, so the grenades are thrown too hard. Guess what. THAT'S NOT THE PHYSICS ENGINE. It's just the way they coded the grenade. Go find your nearest modder, I'm sure he can fix that for you.
Monster AI? No, it's not as clever as Far Cry - nor do I think it needs to be. Maybe the reason the Mancubus doesn't run for cover is that it doesn't think it has to.
As for the spook wearing off in a couple hours of play - I keep hearing that, and I keep waiting for it to happen. I haven't finished the game yet, but it's still spooking me pretty well from time to time. I think the problem is that some design aspects (darkness, etc) annoy some people, and once annoyed it's hard to fall into suspension of disbelief and be scared. But when that body that knew was -there- is now hanging from ceiling, I'm sure pausing for a second.
Scaring people in games is HARD. Scaring people in movies is pretty hard. My GF is notorious for sitting through hair-raising flicks and not blinking (meanwhile I'm jumping out of my seat). Some people just don't bother to turn their heads off a bit and enjoy the ride. Only a handful of games (System Shock 2, AvP come to mind) have really managed to scare me, and just adding Doom 3 to that list is worth the price of admission.
And speaking of SS2 - yes, that game was deeper. Yes, that game was scarier. A shame it also had some horrible gameplay decisions that more or less ruined the game for me. Who puts infinite monsters with finite ammo in a game that expects to explore levels repeatedly? A game that expects you to cheat, and cheat hard, that's what.
Doom 3 offers up one of the most intense, graphically pleasing, vibrant in terms of both actions and environment, gaming experiences I've had in a long time. It's precisely what Carmack said they would do - a revamp of a gaming classic with all sorts of modern splendor tossed on top of it. I feel like I'm playing an old favorite while at the same time enjoying one of the most powerful game engines on the planet.
Gee, yeah. There's so much to hate there