UFC legend Chuck Liddell says watching a Floyd Mayweather fight is a SNOOOOOZEFEST ... telling TMZ Sports he can't stand bouts where guys aren't trying to destroy each other.

Chuck was at the Arclight Theater in L.A. when he told us he respects Floyd -- "he makes a lot of real good guys looks stupid" -- but says his fighting style basically puts him to sleep."

"I'm not a big fan of guys that go out and just score enough points to win a round, Chuck says ... "I wanna watch a guy go out and try to take someone out."