I love the PSP more than anyone, but even I have to admit that it was a mini port machine. Sony marketing VP John Koller admitted as much in a recent interview with Gamasutra:
"The issue that happened with PSP is we got overrun with ports," he said. "It became very difficult for us to define what made PSP unique. The content development became a bit unstructured or decentralised, in that we got a lot of content that was on PlayStation 2 and got thrown over to the handheld."
He continued that the lesson here is that portable games aren't "something consumers play because they've left the living room. It's something that [needs to be] unique, and defines the Vita experience."
So, with the Vita they're committed to "console-like games on portables" and are pushing developers in that direction.
So far, I think they're on the right track, even with some of the launch window containing ports. We just need more games. That was another PSP problem.