Sony would have been smart to have its most successful franchise availible day one. Gran Turismo Vita, an updated version from the PS3 with new vehicles and new tracks. Not a new engine or such they could have put together a decent GT game in a year or so and it would have the potential to sell far greater then any of the other franchises. Not to mention Sony could have utalized the track pad on the back as a steering wheel making the Vita version unique and appealing to the PS3 fanbase.
But I agree Sony's first party software simply lacks the ability to deal a blow to Nintendo. Even during the PSOne days few Sony first party titles out performed Nintendo's titles by much. Despite having over a 100 million hardware units on the market Sony's software failed. I think if Vita is to succeed at challenging Nintendo , Sony needs the third party support Nintendo has lost. That means the western studios, but they also need to go on the offensive in Japan as well.
With Monster Hunter no longer exclusive Sony needs a big Japanese title that Nintendo doesn't have. If I were Sony though I would focus 70% on Europe where my brand is strongest. The remaining 20% Japan and 10% North America. Of course port all the titles across all regions but pour most of their resources into the market where they stand the best chance of winning!
Sony needs to work on defending and expanding its market share where it is strongest rather then evenly distributing its money or giving each region equal attention. Europe should be Sony's highest priority with Japan second and North America last. Maybe Sony should even consider outsourcing some of their work in North America to cut costs there. If I were Sony I would be putting every dime I had into securing Europe and keeping Nintendo at bay. Focus on the other regions once you dominate one!