opening

There is no best opening. All of the main openings are fine if you understand what is happening and what you should be trying to do. 

TINSTAABO

"There is no such thing as a 'best opening.' Each player should choose an opening that attracts him. Some players are looking for a gambit as White, others for Black gambits. Many players that are starting out (or have bad memories) want to avoid mainstream systems, others want dynamic openings, and others want calm positional pathways. It’s all about personal taste and personal need.
For example, if you feel you’re poor at tactics you can choose a quiet positional opening (trying to hide from your weakness and just play chess), or seek more dynamic openings that engender lots of tactics and sacrifices (this might lead to more losses but, over time, will improve your tactical skills and make you stronger)." - IM Jeremy Silman (January 28, 2016)
https://www.chess.com/article/view/opening-questions-and-a-dream-mate

The June 2019 issue of Chess lists the top twenty openings compiled from a list of 1940 April games where both players were rated over 2400 Elo. One can not take position on this list too seriously because it is greatly influenced by how the openings are grouped. For example, all the Retis are grouped together, while English is separated into 1...c5, 1...e5, etc. Nevertheless, for what it is worth, some of the list entries are: 114 Retis, 89 declined Queen's Gambits, 83 Najdorf Sicilians, 75 Caro-Kanns, 73 King's Indians, 61 Nimzo-Indians, 53 1...e6 Englishes, 48 Slavs, 47 1...c5 Englishes, 46 1...e5 Englishes, 43 1...Nf6 Englishes, 43 Berlin Ruy Lopezes, 39 Giuoco Pianos, 37 Catalans, 36 Classical Gruenfelds, 35 Queen's Indians, and 33 Sicilian Kans.

"... A typical way of choosing an opening repertoire is to copy the openings used by a player one admires. ... However, what is good at world-championship level is not always the best choice at lower levels of play, and it is often a good idea to choose a 'model' who is nearer your own playing strength. ..." - FM Steve Giddins (2008)

I agree strongly with kindaspongey's comments. To be honest, I don't even know any openings by name. When I learned to play, almost 50 years ago, we didn't learn actual "openings." We just played. 

At my age it's very difficult to try to memorize openings and the lines that flow from them. BUT, I  find that picking players that I like and playing over and over the games with their favorite openings helps me understand the ideas behind those openings.

Gaining an understanding of underlying concepts is, to me, the most rewarding part of my chess life. It's like looking at a painting and understanding the artist's state of mind when he or she painted it.

Books like First Steps: 1 e4 e5 and First Steps: Queen's Gambit
https://www.newinchess.com/media/wysiwyg/product_pdf/7790.pdf

https://chesscafe.com/book-reviews/first-steps-1-e4-e5-by-john-emms/
https://www.newinchess.com/media/wysiwyg/product_pdf/7652.pdf
can be used as sources of games with explanations intended for those just starting to learn about an opening.

All things being equal it's probably the Ruy Lopez. But all things are rarely equal. It really depends on how well you and your opponent know certain openings. If your opponent is an expert on the Ruy Lopez and you're not, you're better off playing another opening that you know well that they don't. Good luck in guessing the right opening.