I feel like the bigger brand as of right now is Pokémon. They are both iconic, though. They have both had undeniable impact in the gaming industry and outside of the gaming industry.
As much as I love Pokemon, the Super Mario franchise is definitely more legendary than Pokemon. It popularized the side-scrolling genre of video games. The Super Mario games are also more critically acclaimed.
Super Mario is more legendary. Pokemon has had its major impact, but the way Mario has transcended generations so effortlessly without missing a beat has been immaculate and I can't see too many video games or characters doing it. Pokemon is more of a nostalgia thing nowadays.
I personally prefer Pokemon by far, but I'd have to say Mario. Super Mario Bros was a huge help in reviving the video game industry and without it, Pokemon or any other modern franchise probably wouldn't be around.