I disagree, outdoor + terrain can look great in games. Not if you have lazy modellers and are satisfied quickly, but if you take some effort, games can be really great.

Take Uru as an example. Nobody was happy with this 3d non-photorealistic puzzlegame variant of Myst, but it was still beautiful. They made a whole MMORPG out of it with various ages, lands and since it's only about exploring and finding new stunning areas, the focus was on the level design.

Crimson skies for the xbox was also very beautiful IMO. You're flying in airplanes and zeppelins, so yeah, everything is outdoors and quickly reachable. But still, it looks wonderful. Nothing is repetitive.

So it cán be different, just not for all games.