Nintendo no good at mature games
Wii has played host to a number of family-friendly games and that's because Nintendo admits to specialising in this type of content in lieu of the inability to create compelling mature games.
Don't take our word for it - Nintendo of America CEO Reggie Fils-Aime said as much in an interview with IndustryGamers. Specifically, Fils-Aime pointed to BioShock 2 as an example of the kind of games Nintendo isn't good at making.
And we also recognise that we don't create that type of content ourselves. We're not good at it and it's not a key focus area"
While Metroid: Other M is being billed by Nintendo has a mature title, Fils-Aime's point underscores the difference between games like it and more elaborate hardcore titles such as BioShock 2 and Assassin's Creed II.