Which is the oldest game you're still playing today :)

Lol Socom 2... what other game has its longevity. If only they made a new one...hhmmmm

Personally I'm still getting a lot of enjoyment out of Command and Conquer: Generals (2003) as well as Grand theft auto: San Andreas (2004)

Does Neopets count? I logged into my old, OLD account the other day and was hit with the nostalgia

does age of empire count? even if it's remastered? :D

I play Warcraft 3, it's avery old game but it still has 10k+ players everyday online

CS:GO and Gmod are currently two of my favorite right now

Does consoles count? If so, I still play some PSOne games like Final Fantasy Tactics, Megaman x4, x5 and x6, and old versions of Guilty Gear

Skate 3, the best skate game that has ever been made, and is robbed for a continuation

If you mean actively playing online, then it would be Day of Defeat. Just in general, something from the NES era, probably Mario Bros 3.

Definitely Minecraft, can't get away from it. I've been playing it since I was a kid when it came out and casually stop playing for months, but always find myself back to it with a bunch of friends.