Tough question really. If Sony were just a games company, it'd clearly be Nintendo, however they have a lot of other things bleeding money.
At the same time however, they have the option to spin loss making sectors off, as they are doing, whilst having a highly successful video game division.
In comparison on a gaming front Nintendo has a strong handheld format, and a near dead home console. Sony is pretty much a perfect mirror of that, however software sales on home consoles are generally far better meaning, from a gaming only perspective, Sony currently has the rosier horizon.