Exactly, Sony coming out saying "derp PS4 will be teh best graphically" means shit. Vita has proved that. It's about the games implementation of gameplay.
Good point, but here's something else to consider: The PS3 was mostly loved by its fanbase at the time of the Vita's launch. Many Sony fans didn't see the NEED to spend $250-$300 USD on what was quite literally being marketed and pressed as a "handheld PS3" by many reviewers ("OMG IT HAZ PS3 GRAFIX, HURRDURR!!"). They didn't see the need to "carry their PS3 with them," basically.
Wii, however, has fallen into disfavor even among Nintendo fans lately. The 3DS was something fresh and new, which was welcomed.
Also, remember the 3DS was able to bank on the success and popularity of it's predecessor. The PSVita wasn't able to do the same (the DS outsold the PSP by what, like 10x or something?).