I loved Doom!
Running around blasting demons with the coolest-sounding shotgun... ahh, the memories!
No game has recaptured the atmosphere of the original Dooms - It was a weird mixture of insane-hyper-adrenaline filled blast-fests with suspense building bits thrown in. And the Maps!
Say what you will about Romero, he made some great maps for that game. I tend to find most modern FPS maps tend to be, well, samey, uninspired and generally unimpressive.
The main exception is Half-life, that also had great maps.
Doom 3 is a bit false: It is gonna have very little to do with the first two, and in fact usurps the plot from them!
D1&2 were fast-paced action-packed shooters, but D3 is gonna be a slow-paced atmosphere-shooter, more akin to System Shock, or Thief, or ahh crap what's that game... Silent Hill? Alien vs. Predator? (Well, when you are playing a marine

)
It will be one seriously awesomely scary game, but people expecting the next Doom are gonna be disappointed I reckon.
I won't buy it until the Linux client comes out 'tho, since they say Win98 isn't supported
