Penn/St. Pierre II
Honorable mentions to a lot of fights that never happened but sure get talked about a lot. Fedor/Couture, Silva/St. Pierre, Fedor/Lesnar
Oh and Silva/Sonnen I and II. Man the threads were insane.
"You seem to have a very enlightened opinion. Just curious why it's so obvious to you what the answers are."
"Just the stereotypical, ivory tower, pre-law, leftist 20 year old."