What is the best defence against Ruy Lopez?
I certainly don't have the level of Ruy Lopez experience of other commenters here, but I offer one variation for consideration, the Archangelsk and Neo-Archangelsk variations.
I've played 1...e5 as an answer to 1 e4 only once in years because I looked at a daily opponent's record in the chess.com opening explorer and saw he lost to Black something like 5 out of 6 games against the Ruy Lopez. I won. I used the Morphy Defense (3...a6) Neo-Archangelsk Variation (4 Ba4 Nf6 5 O-O b5 6 Bb3 Bc5) because I liked my King's Bishop on the a7-g1 diagonal, pointing at key square f2 early on, following the fourth of Fred Wilson's 4 Principles in Simple Attacking Plans: If possible, point all your pieces at your opponent’s king. Note that the 6...Ba7, the Archangelsk Variation, has a similar theme.
Anyway, we got here after 8 moves and it's a playable position. Both sides have Bishops aiming along the same mirror-image diagonals, Black has two Knights on good first-development squares.
Possibly helpful:
Starting Out: Ruy Lopez by John Shaw (2003)
https://web.archive.org/web/20140627024240/http://www.chesscafe.com/text/hansen53.pdf
First Steps: 1 e4 e5
https://www.newinchess.com/media/wysiwyg/product_pdf/7790.pdf
A Spanish Repertoire for Black by Mihail Marin (2007)
https://web.archive.org/web/20140626195205/http://www.chesscafe.com/text/hansen102.pdf
The Berlin Defence by Igor Lysyj & Roman Ovetchkin (2012)
https://web.archive.org/web/20140627104938/http://www.chesscafe.com/text/hansen159.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/7076.pdf
The Ruy Lopez: A Guide for Black by Sverre Johnsen and Leif Johannessen (2007)
https://web.archive.org/web/20140627023224/http://www.chesscafe.com/text/hansen94.pdf
Bologan's Ruy Lopez for Black by Victor Bologan (2015)
http://www.sjakkbutikken.no/produkter/bologans-ruy-lopez-for-black/
https://www.newinchess.com/media/wysiwyg/product_pdf/9016.pdf
Play 1 e4 e5! by Nigel Davies (2006)
https://web.archive.org/web/20140626201436/http://www.chesscafe.com/text/hansen80.pdf
https://web.archive.org/web/20140627083715/http://www.chesscafe.com/text/hansen98.pdf
The Berlin Wall by John Cox (2008)
https://web.archive.org/web/20140627050257/http://www.chesscafe.com/text/hansen115.pdf
Attacking the Spanish by Sabino Brunello (2009)
https://web.archive.org/web/20140627105306/http://www.chesscafe.com/text/hansen124.pdf
http://www.qualitychess.co.uk/ebooks/Attacking_the_Spanish_excerpt.pdf
The Ruy Lopez Revisited by Ivan Sokolov (2009)
http://dev.jeremysilman.com/shop/pc/Ruy-Lopez-Revisited-The-p3765.htm
https://www.newinchess.com/media/wysiwyg/product_pdf/931.pdf
Fighting the Ruy Lopez by Milos Pavlovic (2009)
https://web.archive.org/web/20140627105306/http://www.chesscafe.com/text/hansen124.pdf
Slay the Spanish by Timothy Taylor (2011)
https://web.archive.org/web/20140627040230/http://www.chesscafe.com/text/hansen146.pdf
The Kaufman Repertoire for Black & White by Larry Kaufman (2012)
https://web.archive.org/web/20140626221508/http://www.chesscafe.com/text/hansen162.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/955.pdf
Grandmaster Repertoire 13 – The Open Spanish by V. Mikhalevski (2013)
http://reviews.dailychess.org/grandmaster-repertoire-13-the-open-spanish-qualitychess-by-v-mikhalevski/
https://www.newinchess.com/media/wysiwyg/product_pdf/7234.pdf
Anti-Spanish. The Cozio Defence by Alexey Dreev (2014)
Playing 1.e4 e5 - A Classical Repertoire by Nikolaos Ntirlis (2016)
https://www.newinchess.com/media/wysiwyg/product_pdf/7572.pdf
http://www.qualitychess.co.uk/ebooks/Playing1e4e5-excerpt.pdf
The Spanish Main Road by Evgeny Solozhenkin (2016)
https://www.newinchess.com/media/wysiwyg/product_pdf/7595.pdf
The Zaitsev System by Alexey Kuzmin
https://www.newinchess.com/media/wysiwyg/product_pdf/9036.pdf
The Schliemann Defence: Move by Move
https://www.newinchess.com/media/wysiwyg/product_pdf/7797.pdf
There are about (roughly) 20 good variations for black against 3...Bb5.
If there was a best one, everybody would play it but at high level, u could see that they play several variations.
Morphy defense is if exchange, take with the d pawn and fork the e pawn and knight. the knight either has to move or defend with the f pawn, which is also bad.