I just want to repeat that I haven't yet seen Monsters vs. Aliens
in theaters yet. So, my description of the story may not be the most accurate, but it starts with a normal woman named Susan who is struck by a meteorite on her wedding day. The radiation from the astral rock transforms her into a nearly 50 foot tall unstoppable force called Ginormica.
She is then abducted by military general W.R. Monger, who is in charge of a secret organization of monsters. These are government monsters living in captivity and they soon realize that they are humanity's last hope against an alien menace.
Each of the four chapters follows the same formula and each of the three characters has their own time to shine in each level. Basically, each chapter poses the same premise. A giant robot breaks free and Ginormica, The Missing Link, and B.O.B. have to save the day the best they can. Each member of the team has a very specific role they play in tackling the giant robots.
Ginormica is usually first and she skates her way to success roller-derby style. Each of her levels is a time trial skating sequence where the speed is already determined, but you have to avoid threats and obstacles. Occasionally, you can jump and pull off a few tricks to make it snazzy, but you are really supposed to be making it to the end as quickly as possible.
The Missing Link is easily what most people will take away from Monsters vs. Aliens. His sections play more like a brawler and combat game than anyone else's. He has some simple combos in his arsenal and he can usually be seen climbing the side of each level's giant robot. While The Missing Link may be a half ape/half fish, he is most certainly all mechanic because he removes screws and bolts from the side of each robot to disable certain weapons and key pieces. Although his sections are simple and repetitive, there is some enjoyment to beating the crap out of baddies and watching them explode. The best thing about his levels are the variety, one minute you spend beating up a set number of baddies before you can progress and the next you are avoiding laser fire in an old-school tribute.
My favorite moments are B.O.B's levels. Straight up old school platforming, B.O.B's gelatinous body can slip and slide his way around the levels and solve various puzzles. Occasionally his levels have a 2-D perspective and it then becomes more like a Mario or Mega Man game. The ends of his levels are the most enjoyable. B.O.B. fights a boss by standing on a plasma plate so he can shoot plasma bullets. If you take Gradius or the Gummi Ship sequences from Kingdom Hearts and mix it with Time Crisis, then you have B.O.B's shooting sequence.
The amazing thing about each level is that it supports drop-in Co-op. Press Start on a second controller and Player 2 controls the anthropomorphic Dr. Cockroach. Although he doesn't do the fighting directly, he has some special gadgets to dispense of the enemies quickly. It is a great addition for families with multiple youngsters.
I hate to say that only 10 year olds will enjoy Monsters vs. Aliens, but it is fairly obvious who they are catering to. During each level, you are supposed to be collecting DNA molecules that act as currency in a bonus area called "The DNA Lab." In the lab, you can use your points to buy concept art, power ups and unlockable mini-games for a good distraction. It equals out to roughly a little more than one mini-game for each level. So there are 25 levels in the main game and about 30 - 35 mini-games available in the lab. I think the only people that would try to collect everything are also the only people that had to have someone bring them to the theater to watch the movie. I'm not saying you can't enjoy it if you are over 10 years old, I certainly did, but I wouldn't blame you if you wanted to get through the game and never touch the mini-games.