For starters, PlayStation Vita has games. Lots and lots of them are in development. Games sell devices like the Vita, and I've played enough of Uncharted: Golden Abyss, Resistance: Burning Skies, Sound Shapes, Gravity Rush, Super Stardust Delta, Escape Plan, Ruin and so on to tell you that you won't have to concern yourself with not having a deluge of quality and interesting games to play. They'll be there, and in impressive numbers. Without games, the PlayStation Vita would be an expensive paperweight with a pretty OLED screen.
For better or for worse, Vita will be pitted against the Nintendo 3DS. But the comparison doesn't make a whole lot of sense, and even if you were to pit them against each other, Vita is still destined to sell better. That's because in addition to games (which Nintendo 3DS is still sorely lacking), it's also a much more powerful machine capable of doing a whole lot more than 3DS