There are lots of people who play chess as much as Kasparov does. Few of them are even remotely near him in skill.

I'm not sure who the best poker player would be, but I've met most of the names that would be thrown out there if you asked the top people, and they're all scary smart. Piano playing is a different type of intelligence than poker or chess, but whoever the world's best piano player is I promise you has a lot of that type.