It's interesting because most Disney & Universal parks have a single E-Ticket that's just so good people will call it the best in the world. At that point, you can pretty much say "Yes, it's one of the very best," but it comes down to personal opinion when you go that far for the single best.
MK has Splash Mountain
Hollywood Studios has The Tower of Terror
AK has Flight of Passage
Disneyland has Indiana Jones
California Adventure has Radiator Springs Racers
Islands of Adventure has Forbidden Journey & Spider-Man
Tokyo DisneySea has Journey to The Center of The Earth & Indy
Tokyo Disneyland has Hunny Hunt & soon B&TB
Hong Kong has Mystic Manor
Shanghai has Pirates (& Tron)
I really don't think Six Flags, while a great addition to the park, even comes close to any of those rides with battle for metropolis. It's not bad, but it's definitely a long step down. It's a great ride for Six Flags though!
Anyway, back to MK's 50th. Interesting to hear the changes.