There is no such thing as 'the best'. Of anything. If there were, it would be the only one on the market.
There's far too much that goes into these types of decisions to overly-generalize lenses into things like 'the best'. Size, weight, filter size, filter rotation, focus throw, autofocus, minimum and maximum aperture, presence of aperture ring, number of aperture blades and their shape, minimum focus, AF focus speed, quality of any AF motor, etc. All of these factors are going to impact your decision, and each will need to be analyzed as to how they affect the results you are wanting to acquire.
Think of it this way. Suppose you were asked "What's the best vehicle?" and you answered "Porsche 911". Ever see a farmer hauling a hay rack with a 911? Or a family of 8 on vacation in one?
And more importantly, your budget. "The best" lens may be $3000, but if you have only $750 to spend, it's kind of a moot point.