When describing something's quality, saying it's the best is much less helpful than a realistic comparison. If you are trying to tout a restaurant's food, proclaiming "they have the best mashed potatoes I've ever eaten" doesn't give the listener a point of reference. What if you've only eaten frozen TV dinner mashed potatoes?
Instead, offer a better than "X" statement. "Their steak is way better than that other place" is still subjective, but at least there is base level from which to judge. But what is even more important to know when communicating quality is the other person's frame of reference.
Do not oversell your product or exaggerate something's quality. The prospective client or your superior may be more discerning than you expect. Compare in realistic terms to objects with shared familiarity. If anything, undersell a product to prevent disappointment.