The very first one you've played -- or at least remember playing? Looking for non-kiddie stuff here -- the first REAL video game, with a dedicated story and non-educational entertainment and such?
For me, it was Starship Titanic. Funny game, great design, weird logic. I finally beat it only about a year ago after an enormous pause. This was shortly followed by Grim Fandango, which I was also clueless at. Didn't even get past the second year until I revisited it so long after my first tries at it -- and I had to be helped to even accomplish that.
Weird games for a three or four year old to play, though. X_x Hehe, to explain, they were my brother's, and I borrowed them for some . . . reason I can't remember. He's just under 10 years older than me -- probably he just showed them to me so I wouldn't bother him while he played Playstation or something.
Whenever I was done I'd play a Sesame Street thing or something. I don't know.
So what's the first non-kiddie game you remember playing? Not looking for any arguments on what really constitutes a "non-kiddie game," and you should know what I mean by that.