The former Brazil international believes the Real Madrid goalkeeper is no longer in his prime and singled out Germany's No.1 as the world's best between the posts
The Real Madrid star, 32, lost his place to Diego Lopez under Jose Mourinho last season and has remained second choice following Carlo Ancelotti's arrival at the Santiago Bernabeu.
In contrast, Neuer won the treble with Bayern last season and has gone from strength to strength since joining the club from Schalke in 2009.
"For me, Neuer is the best goalkeeper in the world at the moment. Casillas is past his best, whereas Neuer is still getting better," Taffarel told Sport Bild.
"The way he plays as a goalkeeper and his technique are extraordinary. Not just in possession, but mainly how he parries and catches shots.
"Someone like Oliver Kahn never had this kind of technique. Kahn was a great goalkeeper, but Germany have had better shot stoppers.
"Neuer is definitely better than Kahn was. I've known for years that he would become an impressive goalkeeper."
The 27-year-old kept 18 clean sheets in 31 Bundesliga appearances last term.