After iTunes let's check Youtube. There the most viewed one by far is Italy's Francesca Michielin with over 16 million views and counting. On the other hand she's extremely popular in Italy backed with this #1 hit from Sanremo and #1 album and #1 hit on every possible chart it seems. Far behind with under 11 million views is Sergey Lazarev, helpd with this amazing video everyone wants to see. Third again someone very popular inhis homecountry with a hge fanbase there, Poland's finest Michal Szpak.
Check how the others are doing here