Why do all the mainstream "gay" movies portray tragedy?

Brokeback mountain, Prayers for Bobby, Milk. It seems like in all those movies the central characters always suffer because they are gay. I realize that the movies like Prayers for Bobby and Milk had a positive message and high lighted our struggle. But for a young gay person watching these movies, it seems to send the message that gay = heartache and early death? Why are only such movies highlighted in the mainstream media?