I guess the number of responses anwers your question, I'd put him somewhere between 15-20 based on ability, potential, star-power and professional accomplishments.
Mayweather Roman Pacquiao Wladimir Bradley Marquez Ward Froch Estrada Mikey Danny Alvarez Adonis Hopkins Uchiyama ...all say "hello."
Golovkin over Kovalev. Geale and Cleverly cancel each other out as far as "best wins" go, but beyond that, Golovkin has the clear advantage simply with the quantity of faded/fringe-contenders he has faced... All of that changes if Kovalev impresses over Hopkins.
Boone Campillo Silakh Cleverly Caparello Thompson Agnew While lacking the name recognition are equal to GGG comp maybe slightly better, especially Cleverly and Campillo. GGG and Kovalev deserve to be at the bottom of that list their positions are debatable.
I believe he's probably the best MW right now but the MW division is far from great at the moment. He's not quite top 10 for me.