If it counts, Nintendo had a pokemon themed amusement park last year, but it was never open anywhere outside Japan. Plus, it was only opened for a couple of months. If Nintendo made a theme park, It would be based on all of Nintendo's francises.
The Mario themed rides would include:
- A large mario roller coaster that tours the entire park.
- Mario kart bumper cars.
- A Glooper Blooper water slide
- A "Luigi's mansion haunted house"
If they made it a joint project, then it would end up being a sub-park within Disneyland. Not that that's a bad thing, mind you.
That would probaly be the most likly thimg to happen if nintendo wanted to make an amusement park.