1. Because Nintendo appeals to lots of gamers more so than the other two consoles.
2. Because there are clearly more casual gamers than hardcore gamers. The HD systems would be the obvious choice for those concerned almost entirely with hardcore games. The Wii has some hardcore games (and more coming) but so many casual and party games (as bad as some of them might be) to appeal to families and a lot more people in general.
I'll come up with something better eventually...







