Google Photos gets my vote. They have simply done an amazing job.
With their amazing image recognition (objects, people scenery), which makes search a breeze. I can lookup pictures from 10 years ago in under 5 minutes. No other product (iPhotos, Picasa, Flickr whatever could do that).
Secondly they have a simple and amazing toolset to make these fun videos and stories. Always awesome to share those with friends after trips or weekends.
Finally, it has the best retention feature I have seen in recent times. It makes these interesting collages, animations or even themed videos of your old pictures/videos and notifies you. Kinda like the moment app but better as it has all your media to leverage. I see myself going back to it multiple times a week. With auto upload turn on it keeps surprising me.
Do check it out if you haven't already.