I think in that Katniss will end up with Peeta because he will never be happy unless he is with her (she's essentially his whole life), where I can see Gale easily moving on. Also, we know more about him than Gale, so the book favors their couple..... It's also kept them alive as of late..... Plus, Katniss realized her true feelings at the end of Catching Fire!

To me, it's not really a love TRIangle, because Gale (in my mind) has never been a contender.

Definetely Peeta, I wanted them together since the book 1! I think Gale has been more of a friend to Katniss than someone she is in love with and the fact that she considered having a life with Gale is cause he is more similar to her (in the lifestyle and all) and it would be easier in general...

But in her heart there is Peeta.

^THIS.

In my Opinion, she never loved Gale...!
She knows him for years, he became in her best and ONLY friend, they know each other better than anybody. BUT she never think of Gale like a lover before the games and Peeta came, for me she was just scared loosing Gale, her friendship and all that.
But with Peeta she always had this Thing, as she said: " “To this day, I can never shake the connection between this boy, Peeta Mellark, and the bread that gave me hope, and the dandelion that reminded me that I was not doomed.”
And when she kiss him,she felt something that she had never felt before, She also feels protected when she is with him. in his arms, his kisses, the way he speaks and undestand her, she is happy with him, in conclusion Peeta is the man in her life