I'd argue that Sailor Moon was nowhere near as popular as peak Naruto. But it was more important because it was the start of the female anime audience.
Yu-Gi-Oh was actually bigger than both of them. That's probably the real 4th tbh.
I dunno... Naruto ran North America for a hot minute, but it didn't put a whole genre on the map the way Sailor Moon, DBZ, or Gundam did.
If we're doing a Shonen Jump Rushmore, then Naruto is DEFINITELY a lock alongside Goku and Luffy, and MAYBE Ichigo.
I could see an argument for Kenshiro (Fist of the North Star), Sakuragi (Slam Dunk), Tanjiro (Demon Slayer), or Jotaro Kujo (Jojo's Bizarre Adventure) replacing Ichigo.