I almost put down “The Spark” for TLJ but while that’s my favorite musical bit in that movie I don’t think you could call it the movie’s theme. Same with Asteroid Field and ESB.
I know, I was just listing my favorite musical pieces in each movie, not necessarily the main themes.
If I had to select the main themes for each movie, it would be:
ANH: Princess Leia’s Theme
ESB: The Imperial March
ROTJ: Luke and Leia
TPM: Duel of the Fates
AOTC: Across the Stars
ROTS: Battle of the Heroes
TFA: Rey’s Theme
TLJ: The Rebellion is Reborn
TROS: The Rise of Skywalker