In comparison to North America and Japan, Europe sees the slowest sales of the multiplayer Mario title.
Despite New Super Mario Bros. Wii being a worldwide success with 14.7 million copies sold, Europe is seeing the slowest sales of the title according to Nintendo data. In an investor meeting, Nintendo President Satoru Iwata explained why he felt this was occurring.

“In Japan and in the United States, video games established its position as a part of pop culture when the original Super Mario Bros. launched back in the days when we were selling Famicom in Japan and Nintendo Entertainment System or NES for short in the U.S. Back then, a lot of people must have enjoyed playing Super Mario Bros. and the fond memories must have remained in their hearts.
On the contrary, in Europe, Nintendo did not have its own subsidiary to market its products, and NES did not spread as widely as in Japan or in the U.S. Because of this background, Europeans may feel less nostalgia for Super Mario than the Japanese or the Americans, which may have caused the comparatively weaker sales of this software so far in Europe.”
Regardless of the sales data, Iwata remains optimistic of the series' growth in Europe.