Pride is like the major leagues and UFC is like the minors.
Now the UFC has some real gems (Rich, Hughes, GSP, etc). But overall the disparity in talent is HUGE. Each and everyone of Prides division are loaded with top fighters.
One knock against Pride from observers though has been the amount of freak show fights they book. I personally love em. And their Judoka fights are a thing of art(something ufc lacks).
UFC fighters make only a small percentage of what Pride fighters make. So the best fighters just chose to go to Pride when they get a chance. UFC is basically in a rebuild mode where they are bringing in cheap($$$ wise not necessarily talent wise) fighters on short contracts. Pride though keeps pitting the worlds best against each other every show, and every year have a tournament or GP where the best from Shooto, UFC, and others compete as well.
Try to get your hands on their last Bushido event, it was maybe the best MMA event of all time. Also look for their MW GP which ended with Shogun winning the whole thing, and also featured the long awaited Fedor vs Crocop fight.