Because I don't really care that much about graphics. Graphics don't make games. We're gamers, not graphicers. Which is why I'll support Nintendo until I die. They make fun games that don't need photo-realistic graphics to be fun. Nintendo started out as a company focused on content. The Sega Master System was way graphically superior to the NES but we all know where that went. Same for Wii. And no, this approach hasn't always worked but Nintendo's software always pulls through.
I don't need amazing graphics to have fun. Which ultimately, should be a game's first priority. Iwata said it best. BTW: Proud owner of PS1-4, and Xbox 360. If I want a console with powerful specs, I have either of those to fall back on.