Black Beauty, Hidalgo, Secretariat, Warhorse and Seabiscuit are four of my favourites. I also have the older Disney one "Miracle of the White Stallions" which has some nice riding in it, but the story line is loose.
I loved National Velvet when I was younger, but I don't know how I'll feel about it as an adult and knowing more about horses than I did then. That does kind of flavor it, doesn't it?
I remember watching the Disney TV movies about horses too. Anyone remember these?
Cristobalito the Calypso Horse
The Horse in the Grey Flannel Suit
Run Appaloosa Run
Justin Morgan Had a Horse
Tonka or A Horse Named Comanche (went under both names)