If I have to pick the single best Disney theme park in the world, it's always going to be the one Walt built — Disneyland in Anaheim, California. It really is different, and better, than anyplace else and the people who run it and work there take special pride in that. But the best Disney Resort in the world, taking into account all its parks, hotels, special seasonal events, and transportation (don't you hate waiting for those buses in Orlando?) has to be The Tokyo Disney Resort. It's has the second best Magic Kingdom style park in the world, with many unique rides. They're really big on seasonal events, too, and they go all-out for Halloween.
Plenty has been written about Cosplay (i.e., "costume" + "play") in Tokyo, but people mostly focus on dressing up as manga and anime characters in Harajuku — on the Harajuku Jingu Bridge; coincidentally right next to the cicadas singing in Mejii-Jingu — and in Akihabara.
Less well known is that for precisely 10 days in early September and 7 days in late October, The Tokyo Disney Resort has official Cosplay days where adults are allowed to come to Tokyo Disneyland in full costume. Here, however, the only costumes allowed are Disney characters (no surprise). These are not the tired schleppers dragging their kids around you see in the U.S. In Tokyo Disneyland there is a regal quality to the care with which the cosplayers make the costumes and the pride which with they wear them. Photos are generally allowed as long as you ask first.
For information about cosplay rules at Tokyo Disneyland, visit the official website (use Google Chrome with automatic translation for best results)