It's pretty much what Cyberevil already said but I have a few things to add.
I have one and just like Cyber, I got it from an impulse of playing Sigma+, that was last July, and since then I've already gotten the same amount of games I've bought for my 3DS, a console I've had since it came out, that was what¿ three years ago¿ The thing is, I can guarantee you the Vita DOES have a lot of very good games.
Ninja Gaiden Sigma+
Ninja Gaiden Sigma 2+
Dead or Alive 5+
Atelier Totori+
Gravity Rush
Uncharted: Golden Abyss
Soul Sacrifice
Little Big Planet
Lumines
Ragnarok Odyssey
...and one of the best JRPG games ever made: Persona 4 Golden.
Then I recommend two titles that while they have their minor issues, are very cool and I enjoyed them a lot: Dynasty Warriors Next and Shinobido 2. Finally, if you're into importing Japanese games that never get localized, you'll be happy to know that the Vita has four great games available over there exclusively:
Tales of Innocence R
Tales of Hearts R (This one is actually close to being released)
Hatsune Miku: Project Diva f
Senran Kagura: Shinovi Versus
Keep in mind that those four are Japanese games, you have to import them from sites like ebay, Play-Asia or Amazon, they're probably expensive unless pre-owned and logically are in Japanese language. And yes, the Vita is region-free, just like the PSP so no problems there.
Then you have digital smaller games like Guacamelee and many others that are available for very cheap and look extremely good and besides, the Vita already plays most PS1 titles on PSN so if you've purchased some for PS3/PSP, you'll most likely be able to play them on a Vita. The 3DS on the other hand only offers NES and GB games as its retro options. Now, don't get me wrong with that last comment, the 3DS is also an excellent machine (dat Fire Emblem) but I think the Vita is slightly better.