I will say it now, I hate motion capture when it's used in the way Monster House uses it: to copy live action frame by frame, movement by movement. It makes the characters seem less animated and more like walking and talking rubber dolls with creepy lifeless eyes.
Motion capture can be done well when used as reference and that only (such as in the case of Gollum in Peter Jackson's Lord of the Rings trilogy). However, when you're trying to directly copy life it comes out basically looking like crap.
That's how Monster House is visually. It looks like crap. The characters look and move very blocky and awkwardly and hardly ever emote... like an actor forced into an elaborate rubber Halloween costume. The "animation" is just above what you get in a video game.
The "monster house" is really the only thing that looks halfway decent... it was actually ANIMATED and wasn't mocapped.
Now, why am I giving it a C+ instead of an F? Because the story was decent and held up fairly well despite the weak visuals.
It's an interesting concept and was executed pretty well.
Story summary from IMDB:
"The teenage DJ is observing his neighbor Nebbercracker on the other side of their street in the suburb that destroys tricycles of children that trespass his lawn. When DJ's parents travel on the eve of Halloween and the abusive nanny Zee stays with him, he calls his clumsy best friend Chowder to play basketball. But when the ball falls in Nebbercracker's lawn, the old man has a siege, and sooner they find that the house is a monster. Later the boys rescue the smart Jenny from the house and the trio unsuccessfully tries to convince the babysitter, her boyfriend Bones and two police officers that the haunted house is a monster, but nobody believes on them. The teenagers ask their video-game addicted acquaintance Skull how to destroy the house, and they disclose its secret on the Halloween night."
It's a pretty original idea. There are, surprisingly, a lot of funny moments. The video game addicted character "Skull" and the two police officers come to mind.
The story behind the monster house itself is a pretty cool concept also.
So, all and all, while not a visually pleasing movie, it was an enjoyable 91 minutes killed and it was, overall, worth the dollar I spent at Albertsons to rent it.
I give this movie a 75 C.