Kennywood, just outside Pittsburgh, PA. Still has a bit of that old time feel to it and some AWESOME wooden roller coasters. It's not all commercialized, unlike 6 flags.
I picked San Diego Zoo because i haven't been to most of those parks.
In reality.....it's more like this...
Disneyland
Animal Kingdom
EPCOT
Magic Kindgom, DCA - tied
Henry Doorly Zoo in Omaha, NE
Adventureland Park in Iowa
San Diego Zoo
MGM (Hollywood Studios)
Six Flags MM hands down. It's a great park for me when I want to step away from the 'magical' factor. Also, if I want to ride some very intense rides, that's the place to be.
Since my brother lives in San Diego, we've gone to the zoo and seaworld (the WAP is so far up if we're driving up there we might as well keep on going another hour and go to Disneyland, LOL). The zoo is huge and hot and exhausting, though amazing, but we like seaworld more. They have such good deals, especially for someone whose brother likes to see them and wants them to visit often. I'm still hoping he'll say "hey I have some vouchers come down!" before the end of the year, so DS and I can use our "fun" passes one more time (bought them last year in early Dec for the price of a ONE day pass, they were good from then through this Dec with only 4 blocked out dates).