Well here's a quick bunch of (apparently) stone cold classics I've not touched. It is merely the tip of the iceberg though.
Half Life 2 - The demo gave me major FOV sickness and that was enough for me.
Deus Ex
System Shock 1&2
Sid Meier's Alpha Centauri
Same. It's supposed to rival Baldur's Gate 2, but I don't believe it.
Battlefield 3 and Call of Duty MW3
Vampire Bloodlines - fired it up once, but need to mod it as I thought it looked bad.
Battlefield 3 and Call of Duty MW3 and Crysis 2
They're all current games, not classics!
arx fatalis for most have never heard of it