Not that I am some sort of expert on this battle, but from my research, if Reno & Benteen (fuzzy on the second dude's name, it has been a while) had showed up with reinforcements and the packs like Custer had asked/ordered them to as opposed to knocking off for the day and talking smack about Custer being a glory hound whist he was being slaughtered he might very well have still won.
Funny thing is I used to totally blame George for his loss based on his conduct in the Civil War, but having found out that his subordinates didn't come to his aid when they could have, now I feel bad for him. I mean seriously how can you blow of a runner bearing the instructions "Come quick, bring packs! Gen. Custer" and then sit a couple hills over talking smack? They should have seen a Court Martial for that in my overinflated opinion, but that just might be me.