Walt Disney World is the most visited park in Orlando. Lake Eola Park in downtown Orlando is the most visited city or county park in Orlando. Thousands visit each of these parks every single day. Although they should be classified differently.
Those parks are visited in that same order. It is surprising and a good thing that Seaworld Orlando is still relevant after all of these years. The park is a little unique and not really an all day park. Much of your time there is spent waiting on shows to start but really in any Disney theme park it's the same thing only different. In Walt Disney World you wait in line for much of your day.
Walt Disney World as a whole is the clear winner. It actually consists of many theme parks all grouped slight distances apart. All of them would be great stand alone Disney theme parks and most who visit Disney World will come for their favorite of the Disney parks. The most visited theme park is still by far the Magic Kingdom. For many though, it is not the most visited theme park twice because they need new attractions. Some popular parts are below.
Disney's Hollywood Studios
Anything Harry Potter
Universal Orlando is a more adult themed location. Universal's Islands Of Adventure and Volcano Bay are my two favorite spots to visit in Central Florida and yes, I live here. The other attractions here are fine for when family comes but my wife and I usually prefer these two parks. Since this is the sunshine state and gets very hot in the summer months all those water rides fit perfectly into my day. Roller coasters and a Universal themed entertainment association knows how to do entertainment.
If you do not live here or have a lot of guests coming in you should consider Walt Disney World Resort or Universal Orlando Resort. Why not make the best of the trip. If a lot of family is visiting them rent a cottage in Margaritaville, Reunion Resort. Try to avoid Champions Gate as there are far better options. See you soon at Volcano Bay but Walt Disney's Magic Kingdom remains the most visited park in Orlando.