it's really hard to tell... if it comes to CASH RING GAMES, there really is no way to track that... but I have seen some amazing players win over $250,000 in a single pot... so it could have millions in their bankroll.
a sure way to find out how they are doing in the Tournaments... is to check out this site:
Official Poker Rankings - Poker Ratings, Poker Results and Statistics
Here you can keep track of their Return on Investment, as well as their wins and losses....
So Far the most Profitable player on the Following Sites are:
FULL TILT
knickadam55 Net Profit of $484,806
ROI = 20%
POKERSTARS
AJKHoosier1 Net Profit of $1,431,751
ROI = 168%
PARTY POKER
TherookieQQ9 Net Profit of $264,630
ROI = 463%
So it looks like the guy from Pokerstars has made the most money in TOURNAMENTS... but we don't know how well he does in CASH RING GAMES.