Who is the best fighter in the UFC?

There are many good fighters in the Light Heavyweight division Forrest Griffin, Wanderlei Silva, Rampage Jackson, Chuck Liddell. The Middleweight division is largely dominated by Anderson Silva as so with the Welterweight division with Georges St. Pierre. The Lightweight division is a contest between Kenny Florian and B.J. Penn. The heavyweight is also a very good division with Brock Lesnar, Antonio Rodrigo Nogueria, Frank Mir, and Randy Couture as the headliners. Who do you think is the best fighter?