Is it having "Mario" in the title?
Yes.
Smash Bros. is not included despite the fact that my dad calls it "Mario Super Mario Smash Brawl Bros Mario" or something like that.
And of course there are plentiful spin-off games without "Mario" in the title which you could make arguments for, like Yoshi's Island DS or Super Princess Peach.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.







