lol Contra? Not only have I beaten it but I even once accomplished the task of doing so without losing a single life. Not an easy goal it was, but an obtainable one nonetheless. (The latter non-Nes Contra games, not so much. Contra: Shattered Soldier on the PS2 is hands down one of the hardest games I've ever played period.)
Anyway, I realize it's pretty much an impossible goal, but I'm a big wrestling fan and was recently giving serious thoughts about watching (and rewatching) every PPV in WWF/E history (as well as possibly every WCW PPV as well) and since I'm an even bigger fan of video games, I wanted to do something daunting of a task there as well. However, perhaps just beating at least, say, 50 or 100 games on each system (which would still consume a good amount of time) would be more of a realistic and attainable goal.