Still Mario. It wouldn't have mattered if Pokemon was even more successful than it actually was in the 90s.
Mario is Miyamoto's baby. That's his Mickey Mouse while he's Walt Disney. At best they'd be co-Mascots. But they would still prioritize Mario in the advertising.
Pancho A. Ovies
Nintendo Switch in Japan (Famitsu): 2018 vs. 2019
PlayStation 4/Xbox One/Nintendo Switch: 2018 vs. 2019