This is a very difficult question to answer considering the fact that Marriott exited the theme park business nearly 40 years ago now.
It's really hard to say what direction they would've gone in had they kept those parks all this time.
I'd like to think that they would've kept more of the original "Americana" theming of the various areas intact, instead of shoe-horning a bunch of incongruous super-hero stuff all over the place like SF did with the Chicago park, but who really knows?
And maybe if Marriott had stayed in the game they would've eventually found a place to build their 3rd planned "Great America" park in the DC area?