Contra

Thanks to the Konami code hehehe

First game I beat? Possibly Kirby's Adventure on NES, or maybe Mega Man 4.

underrated gem tbh

Champions of Krynn on C64 :)

I have no idea what the first game was that i beat roughly 33 years ago. I played many Atari 2600 games growing up, but as we all know, those games had no end to them. I'm guessing it was probably Super Mario Bros on the N.E.S., since that was bundled with the system.

Double Dragon had on the 2600, remember seeing it as a kid after lots and lots of mashing.

First game 100% would probably have been Sonic 2, all the Choas Emeralds beaten the game. In games like Megaman 2+3 on the NES I know I beat them but know also that I had missed some items doing so, god damn Gamefaq's for not existing for another 20 years or so

I'm going to say Monkey island 1 followed by Monkey island 2. A few years later I beat Golden eye, OoT, perfect dark, MGS, to name a few

pinguin adventure on MSX, on console mario3.

I don't remember if I really did any 100% on the Atari 2600.
But my first console one I remember I finished 100% is Mario Bros.
My first Commodore 64 game was Rygar I 100% finished
My first PC game I finished was Police Quest or it was Space quest (I can't recall the year I finished these two and I know the first episodes where close to each other released)

I think it was Sonic 3.