The #1 Pokemon of all time according to snack website Kotaku.com will be a contender in the upcoming Pokkén Tournament game. YES!
Here is Gengar's trailer, which comes from a livestream held earlier today (thanks for uploading the segment, azprojectmelee!)
He will of course be able to mega evolve:
And judging from the footage, his moveset will be heavily based on his actual moves, which is great. Gengar joins the cast alongside critters such as Pikachu, Suicune, and Machamp.
You can watch the full livestream here, courtesy of MaxEzzy:
Nothing major in there aside from a new stage reveal, but the ending is pretty great: