Personally, I can't decide on a single favourite other than Answers. It's so moving given the context of the song within the game cutscene but I'm gonna focus on the more musical themes of the game.

First up would be Fallen Angel, known by most as the Garuda boss theme. The music is a great song that drives you through the battle. The electric organ opening is reminiscent of older Nobuo soundtracks, such as his brilliant usage during the FFVI soundtrack. The guitar that follows brings the music to the more modern games, and boy is it a memorable riff. It's one of my favoured boss themes to date.

My second choice is Twilight Over Thanalan. I don't recall this theme being used as much in ARR as it was in 1.x, but it's one of the game themes that sticks with me whenever I hear it. It's one of Nobuo's soothing and moving pieces of music for those dialogue heavy cutscenes. It's a beautiful piece that I favour greatly.

My final choice is The Sands' Secrets. I love a good piece of rousing music and this theme is strong in that aspect. It really lifts your spirits and makes you psyched for what's to come.

Yes, I have picked all music available in 1.x, I just feel that the original music is better than some of the new arrangements that replace Nobuo's score.