Your "All Time" Favourite PC game?

The Witcher

For people who miss ro, isn't ro2 ob starting soon, if not already?

Grim Fandango. Hands down.

1) Deus Ex
2) Age of Empires
3) Fallout 3
3) Skyrim

(They tie for 3rd place, have played them for countless hours)

Edit: Typo

It's too hard to pick an 'all time' favourite, so off the top of my head here are the games I played the most:

Age of Empires - the Rise of Rome
Red Alert 2
Jedi Knight: Dark Forces 2
Battlefield 1942 (and the Desert Combat mod)
Counterstrike
TIE Fighter

or going way back:
Xenon 2
Supaplex
Battle Chess

I cant pick an All time Favorite PC. Because i usually swap between them when one gets boring.

Here is what i usually go between. Binge Gaming.

1. World of Warcraft
2. Unreal Tournament 99 / 2k4
3. Team Fortress 2
4. Diablo 2
5. ???? Newest Game i pick up

Neverwinter Nights
Diablo 2
Theme Hospital, Dungeon Keeper (love Bullfrog)
Z
Jazz Jackrabbit
Commander Keen (4+)
Dawn of War, Company of Heroes
Warlords Battlecry 2
Elder Scrolls series
Finnish 90s freeware games; Liero, Wings

NWN probably tops them all, it had simply unlimited amount of playability thanks to the great modding community and insane character customization. Fond memories of "Bastions of War"!

There have been many good ones, and here are the most salient in my memory:

Thief
Half-Life series
System Shock
Zone Raiders
Citizen Kabuto
Deus Ex
World of Warcraft
Age of Empires I
Command & Conquer series
Runescape Classic

My all-time favorite game:

Counter-Strike 1.5 / 1.6

The skill requirement of CS is what turned me on the most. I wish it was still a tournament league standard game.

Just recently got into PC gaming a couple of years back, so I'm going to have to say DotA.

I really like Gothic II because of the Atmosphere