The title says it all. Roms and Isos don't count.

For me, it would be SimTower.

The OG "Lego Island"

Not the new crap.

i have some old atari 2600 games but they're my brothers and i dont know where the hell the atari is

Fallout 1
Atari is my brothers so it don't count :P

mario bros.
the old ones

I can't remember what it's called, or what the system is called. But it consists of two players trying to shoot the other with tanks and its all controlled by a little knob.

Same here :o. I'd so play that game right now if it worked on XP... but it only supports Windows 95 and 98. I probably have even older games though, just can't think of them.

I don't own many old games, I'm not old skool like some people in this thread ^^

The oldest one I have is probably a side-scrolling Duke Nukem game

Well that's not an easy question, considering that i have a shelf full of like 150 more or less old games right next to me, but Gobliiins is definitely one of the older ones, the game itself dating back to 1991. That's before i was born. >.>
I'll see if i have anything older, though.

I still have super mario for those birck shaped gameboys xDD