I played DOOM I a lot but only because there was nothing better at the time. Haven't played D3 (I refuse to put up with a slow frame rate and I don't know anyone who has the game) but from what I'm reading here, in official reviews and elsewhere, it offers little in terms of innovation and only the graphics seem to be notable.
I suppose I can't argue with the marketing concept that 'if something sells, why change it' but I expected the guys at id to experiment a little more in terms of game features. For instance, why not have out-door levels where you have to wear a protective suit with limited air supply or use vehicles to a limited extent (would do wonders for the MP game, which I've heard really blows simply because it offers nothing any that other FPSs don't) and expand on the horrer, like trying out new demonic forms--I can think of a ton of stuff that would scare the living crap out of most players and definitely beat the pants off anything offered in Doom thus far...without using rocket-firing skeletons (in fact, that lack of realism makes the wonderful graphics seem almost cartoonish--you're not scared of Mickey right...well, some people are but that's for different reasons).
One thing that tends to get most audiences edgy is grusome torture; remember those half-eaten, still living, bound marines in the original? Hearing screams is fine but eventually you need to see the poor sod being slowly disected in the dim lighting of flickering futuristic lights by some disgustingly horrific, demonic form. This would probably be enough to make most gamers at least sit up a little strighter in that comfy chair.
Also, supernatural events were really lacking in the original (aside from demons spawning out of thin air...but how scary is that). Using D3's physics engine to play with images (e.g. floating objects, warping of objects so that other objects react to them in an odd manner, the images video screens that give you info occasionally warp into screaming faces, reversing of gravity, y'know, all that weird $hit that happens when you eat to much Mexican food) instead of just reddening the screen when the presence of hell gets a little unbearable would make for what I guess you could call a 'creepy' environment (or at least a stoned-out environement).
Nothing ruins a scare more than knowing its going to happen (i.e. you know that there's a good chance that by moving x object, an enemy bot's going to pop out and immediately attack you). Random triggers work fairly well but the thing is you can't make D3 too random because action in this game sticks so closely to the story. Giving demons more complex actions will take up more CPU time and the game's already doing plenty of that.
I think what happened is that designers ran into this wall (i.e. realised that they couldn't make the action tenser within the limitations of the game as they set it up), so they just stuck with the basics of the previous titles and let the cow milk till the hype drains away. This seems to happen all too often in game design and development.
They should have known better because one of the primary complaints of FPS/RPG gamers is that things are too scripted, which takes away from play. You can only script so much until it interferes with the player's enjoyment of the game.
Something that hasn't been mentioned much here is that id spent so much time and energy developing an all-new, extremely advanced physics engine only to limit it to throwing zombies against walls. They raved about it for so long wetting players' appitites (i.e. giving demonstrations of objects realistically bouncing off other objects and things of that sort), you'd think D3 would sport stuff that had not yet been seen in the gaming world.
I was kind of hoping for new, more realistic--but appropriate--weapons too. Like a grenade launcher and flamethower. Instead of limiting it to grenades they could've tried using the Duke Nuke'm trip-laser-activated, wall mounted explosives. So when the baddies try and chase you and walk through the laser they go splat--plenty of fun in Duke. And, keeping with the goriness of the Doom series, what I really wanted to see was innovation in the 'cutting' weapons: the addition of a knife would've been nice instead of a fist...I mean really, what is a fist supposed to do to spawn from hell? Futuristic--but realistic--weapons like a chemical laser instead of that plasma rifle (don't know if this is in D3) would've added to the feel; a cool feature that hasn't really been played with in sci-fi games is a cutting laser (i.e. keep the mouse button depressed and watch the lazer cut the demons into pieces--sounds heavy but the engine could certainly handle it).
I was also dismayed to hear that there is little interaction with other (non-zombie) humans, especially when I read about what they've been doing with HL2 bots.
Some of the backgrounds are quite impressive though--reminds me of looking out at the mountain background in the original (laughable now but it did the trick then). IMO they did a better job on that than the demons. Just that screenshot with the spiders coming down out of a building would be far creepier without the spiders and maybe just something subtle like a camera following you as you move or a person standing at the door watching you only to disappear into the building when you get close. (Not to say that the Lost Souls, for instance, haven't been updated to nicely horrific effect, but the spiders and rocket-firing skeleton...c'mon.)
The biggest problem IMO is the bot limit; 2-3 demons just doesn't cut it--remember that extra level in the original where there's a cage in the middle of a massive courtyard and the moment you let off a round demons swarm out from the various exits.
This is the main obstacle to a successful XP: they can make pretty much any changes because the ground work is already done (like adding new items, demons, even vehicles) but this limitation is something of a brick wall as I see it (of course, I could be wrong and the limitation can be worked around only there was no reason to do so).
BTW, they've started working on Doom, the movie as well. Could be cool...unless they muck it up like most game-based sci-fi flicks. (Hopefully no rocket-firing skeletons.)