I had an idea for a big Nintendo-themed park, so bear with me. It's probably crap anyway.
Main area would of course have to be Mario, probably with Peach's castle (if you're going to go down a Disney route). Mario would of course have to have some sort of roller coaster, probably a traditional one (as opposed to something like Gringotts). Also, a Mario Kart track (I guess it'd have to be weapons-less go-karts) that is really well themed and winds around the area and coaster, and any other attractions here.
Zelda/Hyrule area, with the main attraction here I could imagine being a water ride, Valhalla-style, through Hyrule castle. Don't know what else could be round here as I don't know the franchise that well.
Some sort of futuristic area which would have a ride dedicated to Star Fox (preferably duelling coasters, a la Duelling Dragons - one side for Star Fox, the other for Star Wolf), and also a shooting ride for Metroid (like MiB, Duel etc). Maybe try and get some F-Zero love in there too somehow (now that'd be one heck of a use for Spiderman stuff).
A jungle zone which would have a mine cart (hopefully mostly indoors / in caves) for Donkey Kong, and also some sort of Pikmin playground for kids.
A Pokemon area which has a "Pokemon Snap" water ride. It would mainly be a town or small village, and a new Pokemon game would be brought out in conjunction. Various Pokemon animatronics would be in this area and, if you take a picture of them on a 3DS with the new game, you get to use them in the game.
That's literally all the random crap I can think of.