It's actually hard for me to find a player to compare him to because usually you either have playmaking wingers or the typical modern wide forwards with very clearly defined characteristics but Sancho is really both and I think that is what makes him so outstanding, he is just a very complete player.
I usually refrain from hyping players but if there ever was something like a "Ribery/Robben"-hybrid then Sancho is certainly the closest one I have seen in the last 10, 15 years. The only other comparison that comes to my mind would be someone like Figo who was similarly versatile though I'd say Sancho doesn't have the same technical flair but an even better output (I mean his output is just crazy for his age).
The one area where he needs to improve is that he needs to impose himself more on games (he looked a bit more timid playing for England than for Dortmund imo) but considering his age that's of course asking a lot and I'm sure if his head is right that won't be a problem in the future either.
So considering that some here think there is too much hype about Sancho I actually think he is still somewhat underrated due to Dortmund's role behind us (and thus more limited exposure) and their attempt to not put too much pressure on Sancho.
Except Mbappe I don't think I've seen a more promising teenager (just based on performance, on potential you can always argue that there were others) since Messi/CR.
Terms like "generational talent" often get thrown around easily but Sancho has already created Bundesliga records for his age class and whatever you think about the Bundesliga but even Ribery/Robben at their peak would have had difficulty to produce his numbers:
Ribery's best season was 32 games, 12 goals, 21 assists
Robben's was 26 games, 13 goals, 12 assists
Sancho:
18/19: 34 games, 12 goals, 17 assists
19/20: 32 games, 17 goals, 17 assists
Sancho has already leveled the best seasons of players like Ribery and Robben and that TWO seasons in a row while being 18-20 years old.