I don't know if this has already been said, but I think MH3 features some very beautiful landscapes and sights.
It's been a while since I have done the Ceadeus quest but today I fought Ceadeus and I just noticed how impressive the last map is when you look up to the ruins in the center (fortunately, you can move the camera completely under the character during underwater battles). It'd be interesting to know who built these ruins at this very deep place, but the game doesn't explain much about the world, because, well, the title is "Monster Hunter", eh?
Anyway, what are your favorite sights / landscapes in this game? MH3 is the only MH game I've played, so please stick to MH3.
You like The Legend of Zelda? Then take a look at this! http://www.youtube.com/watch?v=6kpsX5QvT7k
The most beautiful looking map is easily the Flooded Forest. The environments are creative and imaginative, especially in the area near the beginning where you can see the huge ancient pyramid in the background.
The game is full of great environments though so it's hard to pick, every map has at least one area that stands out.