The 3DS does have a lot of great first party content. I decided to wait for the Wii U and play all of Nintendo's first party titles on that system instead of the 3DS. Looks like most people did the opposite
With that being said, I really enjoy the games on the Vita (Ragnarok Odyssey, Persona 4 Golden, Guacamelee, Sound Shapes, Hot Shots Golf, Uncharted). If I didn't have a Wii U, I would be a 3DS owner and state the game library is superior. It doesn't surprise me that some people feel Vita has a stronger library, but it is obvious that opinion is in the minority.
The upcoming games on the Vita look good as well (Ys Celceta, Tearaway, Killzone), so I feel that the system is still being supported. By the time I play those games, I feel I have gotten my moneys worth out of the Vita, so I don't regret the purchase.
I may eventually own a 3DS because Fire Emblem on the 3DS looks awesome and Bravely Default (when it comes over) also looks fun. Based on current sales trends, it looks like it will be the device that will be supported longer term (3+ years) from now.