Wait I thought Mega Pixels don't matter.. :\
It's one factor of many in picture quality. Apple's stance is that other manufacturers overemphasis it, not that it doesn't matter at all.
Focusing only on megapixels when talking about picture quality is like focusing only on clock speed when talking about the performance of a processor. Yes, if all the chips are identical besides clockspeed, then obviously the one with the most ticks per second has the best performance (ignoring temperature and battery concerns), but it's better if you can make it so the chip is able to accomplish more operations in fewer steps rather than just cranking up the clock speed.