Tito is a damn good fighter, period. If both Tito and Chuck fought the exact same opponents, they would both kick some serious ass and look fairly equal. It's just Chuck has his number for some reason, it's probably a mental thing from when they used to spar and Chuck would dominate him. If you watched the last fight, you could see that Tito feared Chuck, you could see it in his eyes. MMA demands aggression, and Tito just doesn't have it when fighting Liddell.
Anyway, Chuck is the man but Tito is also a world class fighter who would be holding the belt if Chuck wasn't around.