That's up for debate I guess because I think Mbappe would fit very well into a top Premier League team as well. That would be the highest competition he can look for in Europe. But I agree that Real Madrid would also be a great destination for him, but it wouldn't be as competitive in the domestic league. Though it would make an amazing attack line for Real Madrid if you combine Mbappe with Vinicius Junior. But when Liverpool one day builds a new team as well, it would be an exciting idea as well, wouldn't it? He could be mainly responsible for a new era in a club.
I think Mbappe will excel in any top European except the German and Italian leagues. These two leagues play very physical football which might affect his soft nature. The English league will be preferably for the French international because the latter is less rugged and plays fast football. And Mbappe has the speed to fit into any top team in the EPL. But from his disposition, he might move to Real Madrid next season. It has been rumored that he has already had an unofficial agreement with the Spanish side. We need to see Mbappe in another league to ascertain his ability to adopt to a new football environment.