In Resident Evil 4 when the gigantic goddamned Salazar robot suddenly chases you. Not so much beautiful as OH GOD WTF RUN AWAY.
In Bioshock when you are in the bathysphere.
In Assassin's Creed when you climb Salah Al'Din's citadel.
In Mass Effect, the cutscene at the end with the huge battle between the Alliance, the Citadel Armada, the geth, and Sovereign.
In Total Annihilation, both of the campaigns' ending cinematics. So fulfilling.
In Far Cry, the entire level Boat. I played it a good ten times through, just endlessly repeating it, exploring it a bit more every time.
The nuke in F.E.A.R.
The scene with City 17 destroyed and the Strider walking through it halfway through HL2:E1.