I find it kind of baffling that Metroid is not better well known. I mean, across all the Nintendo Platforms, there are like 6 Metroid games. Samus has also made appearances in some of the other Nintendo games (or is it just Smash Bros.?). Plus I've also seen on many "Best games of all time" lists has Super Metroid always somewhere in the top 10. Anybody have any idea how well Super Metroid did for the SNES? I mean, if the previous game in the franchise was so incredible, why isn't Metroid Prime selling in the millions? The blame game has to be placed somewhere here.
Oh, and about the OoT sales numbers, gamespot had it at 7.1 million copies worldwide:
[L=]http://www.gamespot.com/gamespot/features/video/hist_zelda/page14.html[/L]
Granted this article was written awhile ago, it was still well after the N64 died.
By simple math, I estimate the following:
2 million in Japan, 1.5 million in Europe, 3.6 million in North America (as Mario said)