The best sim horse game, in my opinion, is Horse Eden Eventing. The graphics in this game are better than most of the other horse sim games I have played and I really like the attention to detail in the game. The basics of the game are pretty much the same as all other horse games you get to buy and sell horses and ponies along with being able to care for, train, breed, and enter your horses into competitions. However, because this is an eventing game the disciplines are limited to cross country, dressage, and show jumping. I don't mind this since those are the disciplines I pick for my virtual horses anyways but if you like western disciplines and not english ones you may want to check out a different game.
Available for: Online
Graphics are: 2d