Holy crap. Watch this person play Marble Madness:
Marble Madness was one of the few games I ever played with any regularity when I was a kid. I played the Amiga version a fair bit and I thought I was pretty good at it. I played quite a few "perfect" games at the hardest level and I was pretty quick too.
If I thought I was good at Marble Madness, all I need to do is to look at this video to understand very clearly that there are people out there who were/are a lot better at it than I ever was.