[kupoartist]

Half-Life, Black Mesa – best city (yes city. It worked liked a city even though it was a research facility. black mesa's total self contained nature was what made it such a groovy place)
Deus Ex – best "miscellaneous" cities
Half-Life – most realistic environments, in terms of believeability (until Xen ruins the game for you)
Unreal 2 - most realistic environments, in terms of graphical power
Tribes 2 – most realistic battle fields (they were massive, rather than detailed though)
Half-Life, Black Mesa- most believeable site for alien invasion
Archimedean Dynasty, Aqua – best fictional world (until Aquanox was released... and i'm not big on fictional worlds anyway)
System Shock Series, Citadel Station / Von Braun - best vision of "the future" (including cyberspace, psychotic computers, dodgy lift music and "the love lounge" on the recreation deck)
Thief Series - best vision of a history that could have happened, but didn't.
Homeworld, The Gardens of Kadesh - Best Hiding place for religous zealots.
System Shock 2, "Body of The Many" - best use of squelching noises and digestive fluids in a location (and not mentioning sphincters either...)

i'll stop now