M rated titles can have a dominant market share. GTA4 has sold over 13 million copies worldwide to date, and is a M rated title.
When the PS3 launched, the most attached title was Resistance (M).
The console is more often purchased by adult males who seek a more in-depth and mature experience than is available from a Wii.
Another example we all know is Halo, which is M rated. Best selling x-box game of all time. the argument that (young) people can't or do not want to play war games is simply unfounded.