Ronald Reagan played Custer in Santa Fe Trail in 1940. Others
include Bugles in the Afternoon (1952); Tonka (1958), a Disney film
about a horse who is the only survivor on the Cavalry side; The Great
Sioux Massacre (1965); Custer of the West, (1967), starring Robert
Shaw. Leslie Nielsen played him on TV, in something called The
Plainsman.
I don't actually know all this on my own - I just looked it up in
Halliwell's Filmgoer's Companion.
Stephen Brophy