I'd argue however that Spotify's song recommendation engine is one of its differentiating factors. I'm always hearing friends rave about how much they love each weeks discovery weekly playlist.
Google Music have been displaying some kind of 'I feel lucky' button for ages (it is not random but based on your listens). They also had artists maps years ago.
Deezer has its Flow
Apple Music has 'for you'
Etc ..
There are many variations in how these recommandations are surfaced to the user though.
I would be hard pressed to recommend one service over another as far as their quality. It is just all over the place depending on your tastes, listening styles and how much new tracks you want to listen to.
IMO Spotify has mostly found a sweet spot in how to present these results to the user.
It seems to me that Google Play Music's recommendations are based on what artists you like, based on machine learning, but not using the actual music, just pattern matching with other people.
I use Google Play Music, and am actually considering trying Spotify to get better recommendations.
Always interested to read more about how these recommendations work.
https://hackernoon.com/spotifys-discover-weekly-how-machine-...