The Game Plan was one of only six films this year to get a pure "A" rating from Cinemascore.
Cinemascore's web site is down, but I assume the other five films are: Code Name: The Cleaner, Are We Done Yet?, Kickin' It Old Skool, Daddy Day Camp and A Mighty Heart.
It also scored well on the college circuit since The Rock is a fave.
Evidently, IT DOESN'T MATTER that it's a silly children's movie!