There was a G4TV show where they showed a history of Doom 3. You can download the video from here if you like: http://www.3dgamers.com/games/doom3/#filelist
Here is a list of download mirrors for the high quality version: http://www.3dgamers.com/dl/games/doom3/g4_icons_doom3-hi.zip.html
The footage comes in three sizes at varying degrees of completeness (only the smallest version has the full intro), resolution, and quality to cater for your available bandwidth.
So you may have to rewatch all three of them to make sure you haven’t missed anything. I’m not going to do that though - the high quality one was good enough.