Defintely, the best position for good anal fuck is doggy style.
Other positions are Ok for a few minutes, but they become boring as they are not so exciting.
It is good also when the girl sits on a guy who fucks her in the ass until he removes his cock, when another guy comes from an upper position and fucks the girl in he ass in his turn ...
It si good also whenthe girl is lying on her belly, and the guy fucks her asshole.
But in many films, we have long moments of the girl sitting on the guys, or beside them, and this is good ass fuck.
When the girl is sitting on her knees and offering her gaping asshole to fucking cocks (or fingers or hands ... ), sucking at the same time this is great !