No doubt Dembele helped PSG win the treble this season, and Dembele is in great form for PSG, but if we compare Dembele to what Mbappe has done in football, both in club and country, I totally disagree with those that are saying Dembele is better than Mbappe. After Dembele has helped PSG achieve great things this season, Dembele is the favorite to win the Ballon d'Or Award, so I totally agree that Dembele may end up winning the Ballon d'Or before Mbappe.
This is where "player fitting a team" thing happens. Dembele was horrible at Barcelona, he didn't even worth the 50 million to be fair, and he never provided anything and he was really causing Messi stress on his last year there. But then when Dembele went to PSG, he started to play better and so far he has been like a superstar and tearing up the world and getting a much better result so far and nearly finishing the whole football trophies he could win.
Mbappe couldn't win here, neither La Liga nor UCL, to be fair he won nothing here, but he scored bunch of goals. Which goes to show you, sometimes no matter how good you are, you may just not get lucky. I wouldn't say Dembele is better, but I would say the gap seems not that big, not as big as we initially may have considered at least.