The characters are cool and all but what got me hyped was just all the modes and additions to improve the Smash experience. They truly are taking the 'Ultimate' title to heart. I remember when Smash 4 wasn't out yet and I was amazed at how much effort seemed to be put into it, but this one is going even further beyond.
Also really happy for Opossum, his dream that became a meme then became a reality. Kinda shocking to me, now with three Awakening characters, but it's clear why it was done. This game is proving bit by bit that it is addressing things people have been asking for, period. Hell I hope they go crazy with the amount of Echoes. Never thought I'd call for more 'clones', but given their presentation and the context of the game, it seems like a great way to go ahead and give a lot of people what they want and try to please as many people as possible.
Only newcomers I'd really be interested in is an Alolan Pokemon, insert FE character here, Rex with Pyra, and a Shin Megami Tensei protagonist.