Well fortunatly there is an huge difference between PS and those so called "games."
WoW is a real industry, you must pay for it, it's a business, simple as that.
Second Life is all except a game, it's a giant supermarket. A lot of "in real" organisation created avatars in second life which generate profits and permit to approach an enormous category of population seating at home, less stressed, more "open". Were not talking of simple nice little games there.