I think Space Invaders...

And the first actual game I played was Wario Land: Super Mario Land 3

Pong, I think

Space Invaders, Atari 2600, 1980

wow I dunno? some crap on Commodore 64 i guess?

PONG emulator or something like that does not count it has to be actual hardware!

I've played Pong on the Atari 2600, as well as Defender, which was my favorite game on that console.

Not sure which game specifically, but it would have been something for the Commodore 64. We had one of those when I was about 5 years old. I remember Bubble Bobble but I'm sure there were some earlier games than that on there.

The Donkey Kong arcade would be the oldest game I've played for real. For now, I couldn't get my hands on an Atari 2600 or Pong console/cabinet.

Something that wasn't a rerelease or emulation Game & Watch Ball I guess (1980).

I'm guessing Combat, being a pack-in with the atari vcs, is my oldest console game... Doesn't get too much older.

If you include arcade machines I may have played older. I'd have to think about it.

Oldest game I've "finished" is probably Pitfall II or Adventure.

Probably Tetris, still play that on my phone from time to time.