It really is no contest. Mario is the most famous name in video games. People who know absolutely nothing about video games will likely know exactly who Mario is - but Pikachu they may easily not know. "Pokemon" is the name everyone will know - that does not necessarily translate to knowing Pikachu.
When your series is named after you that helps a lot in terms of notoriety. It's why so many people who know nothing about video games mistakenly believe Link's name is Zelda - because that's the famous name there. I like to use my parents as a barometer for these things - if I believe my parents, who know nothing about video games and couldn't care less, have heard of them then it's a sign they're really that famous. My parents absolutely know who Mario is, I know they know Sonic the Hedgehog, they probably know Donkey Kong and Pac-Man. But that's probably about it. They'd know the name "Pokemon" for sure, but that wouldn't translate to knowing Pikachu. In fact, I think I recall in my child hood my mother mistaking Pokemon for "Pokey Man" and thought that was Pikachu's name. In a similar way to her thinking Wolverine was "X-Man"
But, anyway, in the case of Mario... even if the Pokemon games were called Pikachu, he'd still have nothing on Mario. I mean, it's Mario. At one point in time he was the most easily recognized fictional character of all time worldwide - beating Mickey Mouse.
