I've said it once and i'll say it again. It takes more skill to win a single disciplined match than a mixed one. In a single discipline (boxing, kick boxing, jiu jitsu, collegiate wrestling, etc.) your options are limited so you have to be greatly skilled to exploit the options you do have. You can clearly measure talent because one person doesn't have something to fall back on that they know better than their opponent. UFC is like letting someone punch in a wrestling match; Its like letting someone tackle somebody in a kick boxing match.

The initial idea was great (kind of a nadal-federer clay/grass court bar bet kind of experiment) but basing a sport around a bar bet is a dumb idea (yeah it makes money but so does meth). Now it is a watered down street fight where somebody has several options to win and skill is hard to measure. A lot of the fights look very amaturish (some outlets more than others) and the concept of the UFC as it stands now is pointless. The only thing the UFC could do worth while is finding a guy who excels at all points of combat or has a fighting style so perfect that he never loses a fight and both of these are impossibilites.

The gracie's won the initial tournament and thats cool hats off to them but they didn't face the best boxer or kick boxers out there at the time. Tyson was well established as a boxing powerhouse by the time the UFC came around and if im not mistaken Vitali Klitschko was a well established kick boxer as well yet they were not in the tournament for whatever reason. The Significance of this is, in a fighting atmosphere where things are multi dimensional, being better on the ground will only serve you well if you can get thru the range that someone in a pure "striking" art can dish out at you.

In the situation where you excel at the ground and your opponent excels fighting upright he has the advantage because the fight starts upright and taking it to the ground means nothing if you can't get thru his ranged punches or kicks. Taking out your opponent in your element before he can even get to his is an advantage that boxers and kickboxers (muai thai as well as suppose) have over someone who is a pure jiu jitsu/ wrestling guy. Cross traing is fine and dandy but theres no way that somebody can become both a master boxer and an excellent jiu jitsu artist or wrestler.

Take any mma fighter and put them in the ring with the rules of any single disciplined arts they have trained in. Against a boxer they lose. Against a kickboxer they lose. Against a wrestler they lose. Against a Muai Thai fighter they lose. Against a Jiu Jitsu guy they lose. Against any single disciplined martial artist (and i'll say this despite the fact that i think a lot of traditional martial arts are unsuitable for combat anyways) they lose if that fight takes place under any single discipline rules.

What you're essentially saying when you say an mma fighter beats a boxer/kickboxer/jiu jitsu fighter under mma rules is that an mma fighter does not have enough skill to beat a guy in a single discipline and can only win if he has an advantage at one thing or another over the other guy. If it stays up the pure boxer/kickboxer/muai thai (striker) wins. If it goes down and stays there, the wrestler/jiu jitsu guy wins. Pure artists have more skill than mixed ones. FACT.