Talking about a "kiss" is not a substitute for a relationship. DC tries and play the two off as a "power couple", but they are playing no part in each others' personal lives. That's what being in a relationship is about. It's the equivalent of kissing a coworker, but you never see each other outside of work.
But again... they're NOT in a relationship. It was one kiss, a single moment and nothing more. It's like a kiss at the end of a first date. You don't know if it's serious yet or even if there will be a second date, but there is enough chemistry to try the waters. Wonder Woman and Superman haven't even been on a date, they kissed seeking comfort from someone they considered an equal, someone who wouldn't get hurt the way they had hurt the people closest to them before. It was nice, which is exactly what the both of them said in Justice League.
As for DC making them out to be a... "Power Couple", that is based on your opinion too I believe. Yes, there has been a lot of publicity around the kiss but that is because, as far as I know and granted I am a new reader to the New 52, it has never happened in the regular DC universe? Is that right. I know there had been one-shots and what-ifs surrounding the possibility, but as far as I know the too were never an item in an on-going title. I think it's unfair for the community to claim that this was strictly for publicity and strictly to sell more comics for a title that has been consistently at the top of the charts week in and week out. Was it meant to have some shock value? Of course! But then writers should ALWAYS be trying new things otherwise stories become predictable, boring, and stale.
And finally, as I said, it was a spur of the moment kiss. There was a spark where two friends/acquaintances realize they have more in common than they realized and it lead to one single moment. To claim there is anymore to it is crazy and it is not implied anywhere in the books. You don't have to know someone outside of work to kiss, you don't have to be best friends to slip into an embrace, as I said before, people kiss (sometimes even more) on first dates all the time and that doesn't mean they call that person the very next day and suddenly start spending all their free time (if they have ANY free time as super-heroes) together. Not to mention that Superman probably shouldn't show up in WW comics because of his weakness to Magic, he could be severely vulnerable around the gods.