Here's an interesting review of "300":
"300" celebrates the male bonding that is found in most war and sports movies. What gives those films their homosexual subtext is less the sweating, shirtless males working together for victory. Rather it's the unstated assumption that unlike the men, none of the women in these men's lives will ever really grasp this singularly important, defining experience. Whatever these men and their future wives share, the women will just never "get it." However, in war and sports films, the men still hunger for a life of normalcy - settling down and raising a family with their female soulmate. But that fantasy of living happily ever after with your true love has little emotional resonance in contemporary buddy films and romances: think The Break Up, Failure to Launch, Old School, Harold and Kumar Go To White Castle, American Pie.
It wasn't always so. In '50's and '60's films, the emotional relationship that men craved was with a woman. Then two films undermined that assumption. For the artier crowd, "Diner" depicted male friendships as deeper than anything that a man could share with a woman. For the mass audience, the same message was abundantly clear with Butch Cassidy and the Sundance Kid. No woman could ever be as perfect for Redford or Newman as they were for each other.
In that sense, Brokeback Mountain wasn't so much about being gay; it was about being male, in ways that women can never understand. Maybe the chick flick has produced its mirror image: the dick flick.