Honestly, I'm not really against the idea of there being ruins somewhere on Mars; it's speculated that there was a time when Mars may have been perfectly habitable. For all we know life could have emerged sooner on Mars than it did on Earth and was extinguished as the planet grew hostile.
However, can we wait to get hysterical about rock outcroppings being possible sphinxes until we actually have humans on the planet?
The rock to the right of it that looks like a clean cut at nearly 90° is more interesting IMO. I think that's also a natural formation. But there's something satisfying about how clean those lines are.