I think more people would have purchased a GameCube. Idk if it would be 20M more, but definitely at least 10M.
Nintendo may not have made the Wii since they could have thought that their sales weren't going to always be cannibalized by Sony. Which means they may have never had those huge sales. Which could mean Nintendo drops out of the home console hardware race sooner and focuses on portability quicker (i.e. No Wii U).
Sony wouldn't have pushed online gaming as much, though it still would have pushed it. PS Plus would have never happened, which means no PS Plus tiers and, of course, no Gamepass.
PS3 would have been MORE successful, and I doubt PS3 would have changed much. Maybe they would have released it later with more RAM?