Even if the intended meaning is that it does (in the title) say "best" not favourite, which is ultimately, if not exactly, a reasonably quantitative question.
I’m pretty sure normally when people express “____ is the best _____ I’ve ever owned”, they’re implicitly saying it’s the best “for my needs and preferences”. Absent brain trauma or serious delusion, I would assume the person speaking is better able to quantify that than any outside observer.