I can't think of a big vita game that would make western gamers want it. But I can think of a few Wii U games that would influence potential buyers. I can't see Vita having a big year this year, but I can see Wii U staying the course, which means that Vita would lose.

China and Japan, let's say "Rest of the World". 
PS Vita is getting God Eater 2: Rage Burst, a new version of the best sold game in Japan and it looks like Rage Burst could even sell more than the original game on the Vita. Games like Sword Art Online Lost Song, One Piece Pirate Warriors 3 and Persona 4: Dancing All Night will help the Vita a lot, the predecessor of them did all quite good on the Vita. And don't forget new games like Digimon Cyber Sleuth, SaGa and Night Cry which all have a lot potencial. "The Rest of the World" loves portable gaming, so Vita will sell a lot units there. I can even see Vita doing better in the west this year than last year, Sony must bring us a Minecraft bundle and localize games like God Eater 2: Rage Burst, Digimon Cyber Sleuth or the new SaGa.

Ok, so you think Zelda, Splatoon and Xenoblade Chronicles X could top Mario Kart 8, Super Smash Bros. and Bayonetta 2?
And why do you think that Vita won't have a better 2015 than 2014? Will the sales shrink without Youtube... xD
And Sony is supporting the Vita right now very good, just take a look in the upcoming games for the Vita!

This is an interesting battle and if the Wii U wins it won't be easy. China will no doubt stretch the vita's lead when it releases there especally when it will get a shit load of games suited to China. in such a tight race that might be enough for the vita. Wii u will probably get a 2016 successor and the vita might never get one. So the vita will probably stay relevant as long as it's supported.

Wii U will outsell the Vita before its life time is over.

WiiU will win, the Vita can't beat it.

Can you think of a big non Nintendo title that would drive sales though beyond Zelda? For the most part, the core Nintendo gamers such as myself are already on board and most of their big guns have been fired.

I think it'll be quite interesting now that the Vita is starting to get an increase of software in Japan. PSV games outselling their PS3 counterparts could well help there too.

Don't get me wrong, both systems will have terrible overall LTD. But I don't think Wii Us overall "victory" if you can call it that is anywhere near as in the bag as some think.

In the end, I think Wii U will be more profitable than Vita, which makes it the more successful console.

No.

Wii U will beat Vita lifetime. Vita is only alive in Japan, and there it's being crushed by the 3DS. There's no contest.

Listen, man.. It's great that you're trying to be positive towards the Vita, but what you're saying is very unlikely to happen!