I personally prefer Super Saiyan 4 - even though I wouldn't classify it as a Super Saiyan stage, more or so a transformation in its own. "Primal Saiyan" is what I would call it. That's what I love about it the most, personally; because it was its own original thing and definitely was a take away from the generic spiky golden hair extension we were so used to seeing. Design wise, it looked extremely bad ass and even though I found the concept of Goku somehow changing clothes and height from the transformation to be a tad bit odd, I looked over it.
Plus, that transformation sequence definitely was the best transformation sequence we've gotten since Goku's first ascension to SS. It was really peaceful and soothing, especially with the smooth instrumental of Dan Dan playing in the background. I loved seeing that hallucination of naked adult Goku reaching out to Earth before the camera zoomed in on his eye and a tear was seen dropping onto the ground.
I've never really been a fan of the whole god concept since Battle of Gods first came into the picture. I personally would've preferred it if the Hakaishin and Super Saiyan God were never introduced. SSG and SSB are both simplistic and boring to look at (even though the auras do look awesome). It would've made more sense if the first SSG was called "Saiyan God" and SSGSS was called "Super Saiyan God," seeing as the first SSG favors Goku's base and the second his SS form. But, whatever -- you can't expect much from Toriyama, who is a rather basic guy himself.
I read that Yamamuro had an entirely different concept design for Super Saiyan God but it was ultimately scrapped for Toriyama's version. 'Tis a shame, I would've liked to see Yamamuro's take on it. Though, I heard it involved the user wearing a cape... Not sure how I feel about that, nor could I imagine it.
It's a tad bit strange how I don't care for SSG or SSB yet I absolutely love SSR.. probably because of its aura (those fuckin' auras, man!). But, yeah. Over all, I definitely say Super Saiyan 4 >> Super Saiyan God, Blue, Green, Purple, White, Rainbow, and whatever else Toriyama pulls out of his ass in the future.