DOOM 3 BFG for PC is bullshit
http://www.tumblr.com/tagged/doom-3-bfg-versus-sikkmod
Been playing with the sikk mod variants for past few days and wow it looks great, but may still brutalize your pc. Still it gives a lot better looks and features over the BFG. Only thing that you might miss is the lost mission.
Have a look at the screens on the above link, then at perfect doom
http://www.moddb.com/mods/perfected-doom-3-version-500
And yes, I'd be lying if I didn't mention that doom3 gets a lot of wrongs, but still if you want to play it I'd suggest that you don't get BFG right of the bat if you really want to play the lost mission.
Rather wait for the bargain bin and in the meantime if you need HD, upgrade and remastered try one of the sikk mods:
http://www.overclock.net/t/1140722/guide-how-to-mod-doom-3-for-insane-graphics
http://mygaming.co.za/forum/showthr...Original-Games?p=704925&viewfull=1#post704925
http://pc.gamespy.com/pc/doom-3/1224919p1.html
http://www.forum-3dcenter.org/vbulletin/showthread.php?t=529711
I'd suggest same route for old doom, doomsday is pretty good
http://dengine.net/forums/viewtopic.php?t=1217&
http://dhtp.freelanzer.com/?page_id=17
PS. Note that doom bfg doesn't support mods or so it seems as fs_game does nothing there is also no option "mods" in the menu...