There are multiple reasons for this, but I think the biggest is that since the NES days Nintendo has very sucessfully built up brands around certain characters, namely Mario, Zelda/Link, Yoshi, Luigi. If you look at the best selling Nintendo games they tend to have these names in the title or a recognisable face on the box art.
Furthermore, Nintendo games can be played by everyone. God of War sold well but no-one's gonna buy that for there 6 yr-old. Mario on the other hand is accessible no matter what age you are and parents would feel happy about buying it for their kids.
I don't buy it that Sony don't have enough experience creating games as a good number are quality titles (Shadow of the Collossus, GT, Killzone2, LBP, Syphon Filter etc.). However, none of them have a historicaly memorable character, and the market for many of these games isn't as huge as age 0-Death. Maybe they need to market their games better?








