Those of us that grew up with gaming may find it harder to be awestruck by what we might consider to be an everyday thing
Are you kidding, the evolution of games from when we started to where we are now, and how much there's still to evolve simply baffles me, just think about it. :V
Also, scenarios. They're the soul of any game, the atmosphere, the fictional world you're diving in.
GTA IV's reproduction of New York, massive yet outrageously detailed.
Ace Combat games and their infinite landscapes, incredibly realistic, specially the snowy maps.
Every inch of Half-Life's Black Mesa, and HL2's new world after the cascade, the Aperture Laboratories in Portal 1 and 2, Valve's ability to create an immersive environment that sucks the player in and makes him forget about reality is endless.
The ruined world in Gears of War, some mixture of futurism and ancient grecoroman architecture.
Ninja Gaiden II(a severely underrated game, unfortunately)'s crazy medleys of towering skyscrapers and ancient Japanese architecture, futuristic highways and medieval canals.
I could go on but I won't, these are a few that make me jawdrop :V