The fact that Sonic was brought back.
Smash tour: just a really poorly constructed mode.
3DS holding the Wii U ver. back: seriously... Imagine in this game wasn't being held back by the 3DS's limitations.
Lack of new stages.
Custom moves: there pretty much a waste, and have died out.
Removal of Snake: why? Even Kojima wanted him back.
Omega Stages: seriously... They actually took the time to create 30+ versions of Final Destination. -_-
So...Sonic is a worse fit for Smash Bros. than Snake? And you think custom moves are a waste?
I feel that the unlock system is a bit bogus, as they're giving too much attention to trophies. Why do they lump equipment and custom moves, two separate gameplay-changing elements, together--and then separately put a thing that's just for completionists or looking at? They also give trophies two modes dedicated to collect them faster (and one of them, oddly enough, is the fastest way to unlock custom moves...). It's like they're deifying trophies, which have existed since Melee, and then leaving their new selling points in the dust.
It's also aggravatingly hard to unlock custom moves, as they're lumped with the thousands of equipment pieces, and you can get repeats.
Why? It's not even like they're completely revolutionizing the game, they're just giving characters ways to be good, and yet it takes so long to ensure that the game doesn't give you another repeat or useless piece of equipment.