One thing I've noticed (well not me but a roomie from college before I got booted) was that the Systems were set up usually so that menial tasks took as much XP/whatever to lvl up as the most complex task. Thus if you were the king Knitter of the world you couldn't fight worth crap.
Then there are systems based on popular books/graphic novels. Marvel, for example, made a RPG with stats for all their characters. Problem was that if you took Daredevil for a spin you couldn't do the backflip, slide down a rail, hit a guy while flipping, and land perfectly. We tried it and DD fell during the first backflip couldn't get up and promply got turned into somthing like cottage cheese.