It's odd that I could have a top three horse racing list, but I actually do:
I enjoyed both Seabiscuit and Secretariat.
And if you need a "trilogy", add in Abbott & Costello's "It Aint Hay", based on a Damon Runyon story.
You might complete the trilogy with the excellent sleeper of a great horse film, "Phar Lap". You wouldn't be disappointed!