Composers who end up with major awards for a particular film have often written great music for films that draw far less attention and so may have underrated sound tracks. Mychael Danna's works come to mind, for instance, with an Oscar and Golden Globe for music in The Life of Pi, but he has scored the music for dozens on dozens of other films as well having written some works for ballet. I prowl around his Apple Music listings sometimes and bump into interesting music for movies I had never even heard of.
As a bonus for being an appreciator of the music in films, once in awhile I do find more movies I like by following breadcrumbs from music credits back to other films by the same sound track composer. That's how I bumped into some of the other movies scored by Alexandre Desplat, after having seen Syriana and liking its music.