What's your pick for the "test of time" award?

CIV 6

X-com: ufo defence )

Heroes of Might & Magic 3

Terraria

Wolfenstein 3D - I was going to pick the original Doom, but I didn't like that I'd have to call it "The Ultimate Doom," rather than just "Doom" (like it should be).

Bully: Scholarship Edition! Not that old, but still, I would easily play it even after 20 years.

Caesar 3

(The original Doom comes a close second, but I'd like to vote for both 1 and 2.)

Crazy Taxi, of course.

I voted for Deus Ex GotY.

motha fuggin DOOM

It's not as old as some of the other games mentioned here but I picked Terraria!

Picked Unreal Tournament GOTY, cause it's insanely fun to play to this day.

Crysis

Unreal Tournament 1999 is a great choice, but as I don't have it on Steam I went with System Shock 2.

This game may not be a "test of time" to most gamers but I have almost 4200 hours in playing Day of Defeat: Source. I am a server admin for a clan that is 10 years old and still going strong considering there's a daily average of only about 600 die-hard players left (http://steamcharts.com/app/300). Mornings and early afternoons are pretty much dead but every night the server is full and we still get applications to join the clan and see new players constantly. It is on sale right now for $1.99/80% off and we are already seeing a slight increase in new players (and people with server or VAC bans trying it again on new accounts) and then it will slowly drop again, but after every holiday or other big sale time we still retain a few cool newbies to keep the game going strong. As long as there continues to be people willing to run dedicated servers I don't see this game ever totally dying. I started playing it when it was just a Half-Life mod and every version up until the current Source one. It has definitely stood the test of time.

Unreal Gold, blew my mind when it came out and still love it, especially for the music.

Portal 2.
But after reading the comments here, I might change it to AoE 2. Played that for years.

i picked borderlands 2

TF2 it will never die and still active today.

Quake 3 Arena, because I'm still playing with my q3a Version I bought in April 2000!

I picked Sonic Adventure 2, since I own it on 3 platforms now, I figured it deserves my vote. :)

I go with Borderlands 2