I think you are asking two broad of a question. If you are strictly talking NLH tournaments, it is sadly probably Phil Helmuth or Johnny Chan. Jennifer Harman is the best Limit hold'em player I've ever seen. I'm a huge fan of Daniel Negreanu, but Antonio Esfandiari is probably the best cash/tournament player. Sure, there are lots of good players out there, but everyone has their own specialty, so try to be more specific in your topics.