There's no such thing as a good gaming mac laptop especially since apple raised the prices even more. You have to spend a minimum of $2600 to get the only mac with a dedicated gpu and it's only a measly 750m. An $800 laptop will blow every single macbook out of the water for gaming. You could max it out all the way spending near $5000 and the $800 laptop will still perform better.
'Average' is what you'll get at best, which would obviously be the $2000 dollar MacBook Pro; the one with a GPU for modelling and video editing and not gaming (Which you could say was present in the earlier models with the 650m)