Neymar was crucial in the treble we won , scored in all important games in CL including the final . Not only he scored , he played amazing. Zlatan did neither of this so i personally don't know what you are aiming for.
Also , Zlatan had the luxury to play with Messi , Iniesta , Xavi all in their prime , Neymar didn't but still had a bigger impact that Zlatan ever had.
I'm also interested who would you exchange the 2nd best player in the world ( when in form ) and the best LW in the world with ?
Apart from that there are some more very important things to mention. Neymar has superstar-status but has always accepted his role of being behind of Messi. More than that these two seem to be quite good friends. Neymar teached lots of people who were afraid of him and Messi in a team a lesson, including Cruyff.
What is more, Neymar is a very professional athlete. Sometimes there is mocking about partying, getting banned for birthday parties etc. However, Neymar is easily one of the fittest if not the fittest in our squad. He runs a lot every fucking game, makes the most off the ball out of MSN and he will be a key part if Valverde wants to bring back pressing. We should not take for granted that a player of his class shows this attitude.
Only two things you can argue about is his finishing and his cockiness on the pitch. The latter makes him a hated player for opposition and their fans, but I don't have a problem with that. Every team needs such players and as long as the team doesn't suffer from it it should be ok. His yellow-red was his first here IIRC and I#m sure he will learn from it. About his finishing. I'm sure it will get better when the team as a whole works better like it did in the last treble-season.
Neymar is what they call a franchise player in the NFL and imo a part of our (unsaleable) core out of ~MAtS, Piqué, Busquets, Iniesta and Messi. I'm confident Umtiti can take over when Piqué retires like Piqué did when Puyol left. Not that I want to sell players like Suárez, Roberto or Alba, but I would consider it if one offers the money they pay these days for players of that class although Suárez is a case in its own as he is kind of the perfect 9 for Barça.