The Naples side advanced to the cup semi-finals courtesy of a 1-0 win over Inter, which came about via Higuain's late winner at Stadio San Paolo.
Higuain ran onto Faouzi Ghoulam's clever throw-in, cut inside Inter's Andrea Ranocchia before lifting a strike above the on-rushing Juan Carizzo to finish into the side netting.
Benitez said the Argentinean, 27, was world class.
"Higuain is a great striker and I think one of the best in the world. I've worked with many excellent forwards, including Raul when he was only 16 years old," Benitez told Rai Sport.
Benitez, who coached Inter for a tumultuous six months in 2010, said the result was not a vengeful one despite it coming against a side who sacked him.
"Tonight we deserved to win against a top level team," he added.
"Inter have exceptional individuals and deserve to be higher up the Serie A table. Just looking at the bench they ought to be challenging for the Scudetto.
"Was I taking revenge? I've faced Inter many times now.
"Everyone knows what happened there, but now we move on. I am in a club where we work well together and all have a good rapport."
Benitez said Napoli's turn in form - they have won six of their past seven - could be attributed to the confidence gained from beating Serie A leaders Juventus in the Italian Supercopa in Doha in December.
"It's possible [the Supercopa has had an effect]. Beating such a strong Juventus side always boosts confidence," the Spanish tactician said.
"Ultimately, belief in ourselves does make the difference."
Match-winner Higuain said Napoli were full value for the result, given their output.
"This team worked very hard and we're in an excellent period of form," the striker said.
"The important thing was to work hard and fortunately today we were rewarded for our efforts, as we tried to win throughout.
"We have improved a lot recently and have great belief. Now we can rest and focus on the next match with Udinese."
