I disagree, they are not even in the same league. Street Fighter IV, plus Super Street Fighter IV and Super Street Fighter IV: 3D Edition have sold together about 6.4 million copies. New Super Mario Bros. Wii on the other hand has sold 27.6 million. Even Super Smash Bros. Brawl has sold more than all the versions of Street Fighter IV combined.
Smash Brothers isn’t competing with the Street Fighter gameplay which keeps Smash safe from competition. Add in the Mortal Kombats, Injustice, Guilty Gear, and all the other various fighting games out there, and you’ll find that Smash is the niche compared to all those games combined.
While Sakurai wouldn’t mind Smash becoming mainstream, his real goal is to make sure Smash remains differentiated from the fighting genre game style so Smash doesn’t lose its sales.
The ‘Nintendo difference’ is bullcrap. The Nintendo difference is all about not competing head on with similar software. In other words, Mario Kart isn’t competing against other racing games.
People say Nintendo cannot compete in hardware competition which is why they differentiate their consoles so wildly. But I’d say this is more true with the Nintendo software. This is why I dislike modern Nintendo so much. In the old days, Nintendo produced sales by making the BEST games. These days, Nintendo produces sales by making DIFFERENT games.
I prefer BEST over DIFFERENT every time. I don’t have much time in the day. I want to play the best, not play every goofy differential take on the genre.