I don't count ports and multiplats, and that goes for any system. A system can have a hundred great games on it, but if you can get them all somewhere else then there just isn't a reason to get the system. The Vita does have the advantage of being a handheld, so one could argue that playing these games on the go is the most appealing part, but I just don't think that's enough. It's the same with the Wii U. Count the number of awesome games available on it and you'll see that it's a great system. Whether or not it's worth purchasing is another story.
Then you've also got to consider that even if a system has a really good amount of "great" games, it might still not be enough because everyone's got different tastes. You've got to have such a huge library that people of all kinds will find plenty that they like. For instance when I look at that collection, then take out all the games that I can play on other systems, then take out anything sports- or racing-related, that leaves very few games, out of which I personally only find one interesting enough to play. To many it's a great collection, but to most people there just isn't enough compelling and exclusive software.
Hopefully someday it will turn around, though. I mean, the PSP was a beast once it found its legs.