I think the first time you take an aircraft high up in Just Cause 2 counts as a 'wow' moment. You can look out over the miles and miles of terrain and realise you can fly to any part of it whenever you want.
Also, that part in Crysis when you first look out over the hill at dawn and the sun is rising through the trees and the bushes. I won't upload a screenshot since it wouldn't do it justice.
Grinnbarr said:
The sound design in Battlefield BC2. When I fired a weapon in a small space for the first time and heard the echo and the sheer noise I was almost deafened. Fantastic stuff.
Oh yes. I once had to take off my headset to work out whose dog was barking behind me. Even after I realised the noise stopped when I took it off, I still didn't believe it was coming from the game. It was that realistic.
Add in the incredible soundtrack and pretty good writing, and you have one awesome gameplay experience.