I agree with what cyco says to an extent. Notice that most of the SF guys are guys that also fought in Pride at one point. The different rule set and fighting in a ring changed the game. I believe under Japanese and Brazilian rules you were forced to be more aggressive. You couldn't lay and pray as guys do in the UFC now to win a fight.
Strikers had an advantage due to kicks and knees due a downed opponent. Takedowns had less value and you weren't able to win a round by pushing a guy against the cage and just holding him there. Yellow cards for stalling, more frequent standups, the list goes on and on. As far as the actual rules of mma go, I think the sport has devolved.
All other sports have changed the rules over the years to make the game more exciting and usually faster-paced. Forward pass in football evolved to less contact on the receivers opening up the passing game. The shot clock in basketball and a crackdown on hand checking. Meanwhile, mma under the Unified Rules continues to take away weapons for a fighter to finish a fight. Just my opinion, but that could be another thread in itself.