More people would recognize Mario. Which is impressive, because everyone knows what a Pikachu is.

Hard to say. Some people act like Mario is still as huge as ever but I see more and more kids not playing his games before I showed them XD In terms of general population, the 12 + crowd are more likely to recognize Mario whereas the 12 - (newer generation) crowd will more likely know Pikachu. In a few years I could see Pikachu being more recognizable easily

For gaming, easily Mario.

People are debating who's more popular, but there is a reason why Link is the most bought Amiibo...

OT: Pikachu is like the Buzz Lightyear or Woody of Nintendo, while Mario is like MICKEY MOUSE of Nintendo (or the Mickey Mouse of VIDEO GAMES... period). Like Toy Story is to Disney, Pokémon is to Nintendo... but it's still not the Franchise like Mickey Mouse/Mario...

Mario, no doubt, especially in Japan. There is a lot of merch of the characters here. It's kinda crazy actually.

Mario by FAR.

Mario, but wow... the things we get threads about. Is this for a school essay, or validating something or what? What is the purpose of knowing if Mario or Pikachu is more iconic?

I'm writing my thesis over it. 

My internet connection sabotaged my thread making skills. 

For crying out loud, it's Mario. Comparing Mario and Pikachu is like comparing Mickey Mouse and Naruto. Sure, a lot of people know who Naruto is, but EVERYONE knows who Mickey Mouse is.