Well God of War has a bigger fanbase than all of Sony's other IPs by light-years, over 4.3 million fans on the FB fan page which is more than double the 2nd biggest Sony IP, so if they create a great quality exclusive God of War game for the Vita it will entice millions of GoW fans to buy a Vita which will help a lot, probably more so than Gran Tursimo would since that franchise isn't nearly as beloved or popular as GoW, without mass bundling I doubt it'd be much bigger. Although as some people have said, one game alone won't make a big enough impact no matter how good it may be.
Aside from a GoW game or to a lesser extent a fully featured GT game, what the Vita really needs is an exclusive (even temporarily) Grand Theft Auto game and something that'll be popular in Japan. If they release all these games and they are of a high standard then the Vita could start doing very well, first it needs a price cut though.







