I've known, for a very long time, what #1 had to be. It's simple to make. It's a solid game style, that consistently sells. It's a niche that's not even close to being filled - there's only one competitor, really, and that series isn't released often.
On the other hand, that particular series is one of the Goliaths of the gaming world. It's not as big as Mario. But if you asked someone to list the best-known franchises, it would probably be up there in the top ten.
I just realized that this series has moved out of my niche. My niche is empty. 100% empty. No competition whatsoever, and it still sold well!
Man, I gotta get this thing started before someone ganks my niche.