Obviously it's justifyable to compare the consoles.
I paid about the same for my Wii as for my 360, so expect the same: good games. Personally I don't care about graphics, my Virtual Console gets lots of playtime, but the games themselves are really important. There are good games on all 3 consoles and that's their basic function as a gameconsole: playing games.
They're also in competition for the same costumers. Obviously their markets don't have a 100% overlap, but in general a costumer looking for a gamesystem will make a choice among the three based on perceived value.
The most important part where they are in competition is for developer investments. It's been noted before, but the combination of Monster Hunter and Dragon Quest could basically have saved the PS3 in Japan.
Smaller core franchises like Tenchu, House of the Dead, Fatal Frame, Tales, Sonic (storybook), etc don't do a whole lot on their own, but combined offer a very nice library that would have broadened the PS360 library as well.







