If it was a completely alien creature with vertical eyes, it would be a lot less creepy. I think we have an "uncanny valley" thing going with a dog.

In ancient ocean creatures, bilateral symmetry evolved at the very beginning of higher animals, and everything else pretty much stuck to that.

Prey animals have eyes that go pretty much sideways to see as much area around them as possible. Predators have eyes that go forward, for acquisition and ranging. In the land of gravity, where things move pretty much sideways most of the time, side-by-side eyes work best, even if the bilateral predisposition wasn't already there.

If you were designing something from scratch, it would have three eyes for dimensional resolution in all directions, but evolution works with what's on the table, not with what might be the best possible solution. Life is a series of successful kludges.

It's interesting how sideways 2-D movement is so ingrained in us. Ever notice on Star Trek that the ships usually move in a relatively fixed plane, as though they were seagoing vessels? In one movie, the Enterprise, for once, sneaked up from below, which apparently shocked the hell out of the enemy.