I ran in to this problem this year, too, although my animals are gamey whether it's cuts or ground. I half expected it, because I got a very old whitetail buck and a muley doe. My experience is very much like 121553 on whitetails vs. muleys.

Anyhow, make sure you are trimming your meat for ground as carefully as your cuts. Sometimes people get a little sloppy on the bound-for-ground meat.

I've been cooking my steaks after a long marinade, not usually my choice because I like the flavor of game, normally. For burger, try frying them in bacon grease, this will cover a lot of the gaminess. My muley has a strong brushy flavor that seems to blend really well with garlic salt for some reason. So I have just fried the burger normally with her, then substituted garlic salt for regular salt and that has worked well to disguise the flavor.