My Hero Academia - Smash Bros

Deku: "I'll pick….Captain Falcon!"

Bakugou: "YOU THINK YOU'RE FUCKIN FUNNY DON'T YOU!?"

Deku probably mains Captain Falco since he's the most Superhero-esque of the roster since his attacks have signature names, be it canonical or fan-named.

His moveset is also quite reminiscent of Almight.

As for bakugo, he'd probably be vain enough to pick something simply because their moveset includes explosions.
He'd probably pick MegaMan with a skin that most resembles his own outfit.