I agree with SpitfireS and INDYMAC. Motor oil is not hygroscopic, so unless it gets wet it's fine. The antioxidants in the oil wouldn't be depleted since it wasn't exposed to high temps and no acids introduced (sulfur and carbon - products of combustion).

But if the bottle was sitting in a dusty area that could pick up lots of airborne dust particles, then I'd consider passing on the oil. Not because the oil went "bad", but because dust (especially silicon, which is a main ingredient in most dusts) is abrasive and would cause excessive wear. If it was just sitting in the corner of a typical garage, I wouldn't hesitate to use it.