He's not underrated.
He's the Best player Ever but I will say Mario also was the best player ever. Gretzky pretty much did everything on the ice, creative, fantastic vision. But Mario the moment he stepped foot on the ice he was like in a completly different league and I'm not playing with words, NHL was pro A and he was pro AA where they could have created another league for him. He was a superior being on the ice like when you're a kid and you play with your slightly older brother, you cannot possibly best him. That was Mario in comparison to the other players. Mario was Superman, Gretzky was Iron Man/Tony Stark maybe as far natural talent vs thinking skills(Wayne was known for praticing his shot and new moves all the time).