#1 Kylian Mbappe
Kylian Mbappe has been on Real Madrid's radar for a long time now and he will surely be the superstar signing that will take Real Madrid to the next level. He has been the only competitor to Messi for the Golden Boot as he has scored 29 goals and assisted 15 in 33 games for the Parisians.
Still only 20, he is yet to hit the age when many players hit the peak, and is already dominating the scoring charts. Having played an important in France's World Cup triumph and also helping PSG steamroll through the league which is pretty much done at this point.
If he moves to Real Madrid, there will be much more of a competition than what he faces in Ligue 1 and will reignite the El Clasico and make it more interesting than ever.