There is no "Best" opening per say, think of it as finding a structure you feel comfortable with... ideally something that your opponent is not comfortable with. I like closed openings, so I play for Queens Gambit Declined structures. Tactical players dive into e4 openings like the Ruy and the Sicilian.
The Ruy Lopez is probably the most deeply analyzed opening, some might say that developments here define the frontier of the "best"
What is the best opening for white? What is the best defense for black?