This has been stated before, but it's reasonable to conclude that Sony and Microsoft are after different things than Nintendo is.
Sony and Microsoft are using video games as a trojan to get in to your living room and control other content, e.g. movies, television, music and so forth. In essence, they're imaging a Windows-esque monopoly where a single company controls the portal through which consumers purchase a variety of content.
That is a marketshare driven goal. Whether this ultimately is a lucrative avenue for either of these companies is still unclear, but it's reasonable to conclude that this is what they're after.