The Mario franchise has sold more in the 7th generation than any other franchise sold in the 6 first generation combined. It's ahead of Final Fantasy and The Legend of Zelda combined.
You can claim that Mario's sales aren't so impressive, considering there are 21 of them this generation. Well, can you name a single franchise that has a higher average pr game than 7 million?
A quick check tells me that no non-Nintendo franchise has a higher average sold pr game than Mario this generation, be it for the 7th generation or all of them combined. (Except for possibly Grand Theft Auto, depending on how you count it) (Of Nintendo franchises, it's only Brain Training and the Wii series that beats it).
You cannot evade the fact that Mario games are selling insanely much. Heck, the 6 Mario Kart games are likely to outsell the 16 Zelda games by quite a margin, and they're close to the total of the 61 Final Fantasy games.
Edit:
Oh, you asked a question. 200 million seems rather likely. The already released DS titles are looking at at least another 10 million more (mainly from NSMB and MKDS). The already released Wii titles are looking at 10 million (at least) from NSMB Wii, 5-8 million from MKWii and probably a bit over a million for the rest.
In other words, you're looking at over 175 million even if no more games release.
It is of course possible that Nintendo will cease to release more Mario titles, but I consider that somewhat unlikely. 200 million seems somewhat low-end.
