I'm still playing through XC3 but I think XC2 will remain my favorite of the trilogy.
I enjoy all of them, but XC2 is one of my favorite games and I've returned to it so many times in the last 5 years. Not because I think it especially excels in any one area, but because of a bunch of things I just personally find endearing.
I like that it's corny and obscenely anime, I like that the aesthetic is hyper saturated instead of the slightly more realistic settings and color palettes of the the first and third games, and I found the characters to be really fun and easy to like --they're simple, but that's not a bad thing.
It just hits a lot of my sweet spots in a way that the other two don't hit as well (though I still like them!)
one of my favorite videogames has a giant robot maid girl and I just have to live with that and myself