Turns out that Pixar represented that rare (and by rare, i mean otherwise non-existent) entity that truly learned from its mistakes and only got better with time.
Pixar grew up for this movie, by leaps and bounds. Not content to simply make an entertaining buddy-flick, Monster's aimed for something higher...art. The stakes are high here, with a conspiracy to steal the screams of (ie- kill) all the worlds children in order to develop a more effective way of harvesting energy for the monster world. The main characters must choose at one point between what is right and what is...also right. Sully is confronted by the fact that his life-long friendship with Mike might need to be sacrificed in order to save Boo's life. What a choice!? This profoundly adult dilemma is what gives real danger to the action that happens on screen (and the action is top notch; that race through all of those doors, brilliant!)
Add to that shockingly good animation, humor, and a wonderfully off-beat jazzy score and what we got was proof that Pixar was going to be around for a very long time.