In answer to the thread title, it may have been done before, but I don't remember answering it previously. 
Over the years that we've been married, my wife and I have changed our minds a few times about our favourite positions. At first, it must have been the missionary position because that was the only one that we knew (we were both virgins). As we started to experiment more, we found that we both enjoyed the "naughtiness" of doggy style -- at least, when we could figure out how to get ourselves properly aligned (not as often as we'd like!).
Recently, our favourite has become reverse cowgirl (at least, until my wife's legs get tired!). We both like having both hands free: I'm able to caress my wife's body and assist her hip movements as she rides me, and my wife can touch herself and apply a vibrator (Lelo Siri) to her clit as the mood takes her. It took me a while to persuade my wife to try this position. She was very self-conscious at first, but rapidly discovered that she enjoys taking control for herself of the angle/depth/speed of penetration.
Now, we do reverse cowgirl in front of a mirror so that my wife can watch herself ride on top of me (which she blushingly admitted to finding a big turn-on) while I talk to her lustfully about my views of her (both forward-reflected and rear), the sensations that I'm feeling, and the hot thoughts that are running through my head. This combination of stimuli seems to overcome my wife's residual inhibitions and sets her into flowing and uninhibited sexy motion, which in turn works me up into a frenzy. When my wife has had enough of being on top (usually when her legs ache) we revert to missionary position, with me taking on the workload until we're both completely finished.
Hopefully that explains why reverse cowgirl is our favourite at the moment. 