As noted by others their two main advantages are:
a) breadth of company to draw on (not that they always do it well) - i.e. they own content (Sony Studios) they own various HW elements (TVs, DVD players, BR players, Walkman, etc) and they have both HW and SW for their consoles. Compared to all the other players in gaming right now they are they only one who can serve as a 'one stop shop' and so of course they get the benefit - i.e. while I have a mix of vendors (as do many I'm sure) there will also be plenty of folks who are playing a PS3 on a Sony Bravia with a Sony PSP and a Sony DVD player - and perhaps a Sony digital camera and recorder with a Sony laptop just to finish of the package.
b) they have (historically) the best mix of developers and genres on a single platform. PS3 hasn't leveraged this enough yet (I think its actually too close to 360 right now for its own good but that may be Sony desire to try and gain momentum in US). Next Gen had a good article that raised this point well (as did FinalEvangelion) - the real key to PS2 level sales is a catalogue of games so diverse there is something from everyone. PS3 and 360 don't have this and 360 will struggle most trying to get there I believe. Wii stricltly speaking isn't there yet and is still cruising on its own hype - but I think Wii could also achieve a very broad catalogue too.







