What's the video with the most views on youtube?
With numerous videos readily clearing one billion views by 2018, more interest has been on two and three-billion views and higher metrics. In May 2014 "Gangnam Style" became the first video to exceed two billion views. "Despacito" became the first video to reach three billion views in August 2017, and since has surpassed four billion in October 2017, five billion in April 2018, and six billion in February 2019.
What's the video with the most views on YouTube from 2017?
Despacito
List of most-viewed YouTube videos
No context provided
What's the video with the most views on YouTube from 2016?
Baby Shark Dance
No context provided
What's the video with the most views on YouTube from 2015?
See You Again
List of most-viewed YouTube videos
https://en.wikipedia.org/wiki/List%20of%20most-viewed%20YouTube%20videos
An early metric of a video's popularity was the so-called Billion View Club, denoting videos which had succeeded in reaching over 1 billion views since their initial upload.[2]

In December 2012, "Gangnam Style" became the first video to reach one billion views.[3] By June 2015, only "Baby" had also managed to pass this threshold, but, by October 2015, a total of ten videos had done so,[2] and the number grew further to 100 in February 2018.
List of most-viewed YouTube videos
The music video for "See You Again" was directed by Marc Klasfeld.[33] It was uploaded to YouTube on April 6, 2015.

Background
The "See You Again" music video was the most viewed video on YouTube from July 10 to August 4, 2017,[
See You Again Music video
An early metric of a video's popularity was the so-called Billion View Club, denoting videos which had succeeded in reaching over 1 billion views since their initial upload to YouTube. The music video for "See You Again" was directed by Marc Klasfeld, and uploaded to YouTube on April 6, 2015. Baby Shark Dance uploaded in 2016. "Despacito" became the first video to reach three billion views in August 2017.     