No he actually isnt.
Martial
Rashford
Gabriel Jesus
Yes they are good young strikers with big potential but are they on the same level as:
Ronaldo
Messi
Suarez
Aguero
Salah
Diego Costa
Higuain
Sanchez
Kane
Lewandowski
Cavani
Aubaymang
Dybala
Insigne
Not a chance at present, thats not including players like Mane, Lacazette, Milik, Lukaku, Rodrigo, Firmino, Morata, Alcacer etc.
Rashford has around 20 goals in 91 games for Utd
Jesus is better for City but again its around 1 in every 2.5 which isnt anywhere near the goals the above elite strikers are notching. Jesus will never be a starting player for Man City.
If City are serious about becoming a serious force in Europe in the same bracket as Real, Barca, Juve and Bayern they will need another player like Aguero to fight on all 4 fronts imo.