MK4's sound track was top fucking tier. I could never get into the gameplay when I got it for the PC, but I ripped the tracks and started listening to them and they are really the most well put together.
But MK1's music is still my favorite. Even if just for the character selection screen. MK2 and U/MK3 musics were good but they sounded like arcade game music to me, whereas MK1 and MK4 music sounded like it was composed for the purpose of being music.