>> You can't force someone to sell something they don't want to, especially because Apple is nowhere near a monopoly in games or gaming sales, they can just point at steam.

I think this depends on the basis of the rejection. If you can prove that they are not selling because of discrimination then you can force them. The question how can you prove it.

https://en.wikipedia.org/wiki/Masterpiece_Cakeshop_v._Colora...