Yup, the music in X is very hit and miss. The themes for the regions are great, but any tracks with vocals in them can be grating, especially because they are played often, such as in New L.A. or some of the battle music. Even the people who prefer X over any of the other games should be able to admit that X has the worst soundtrack.
X has my favourite soundtrack of them all, so you cannot make statements like this like it is objective lol.
They all have phenomenal soundtracks, but X really stood out to me. Got me into the composer, and made me an anime fan. Uncontrollable is one of the most epic tracks for combating unique monsters. Great for working out too.
2 is my favourite game though. X second. I am only on chapter 2 of Xenoblade 3 right now, really enjoying it. 1 was amazing. They are all amazing games. I just wish jumping on platforms was better... Makes exploring and grabbing random items on slightly elevated hills a chore sometimes.