Neymar quit Catalonia for PSG in the summer of 2017 for a world-record transfer fee of €222m (£198m/$250m), with Dembele arriving from Dortmund for €105m (£90.6m/$118m) soon afterwards.
Bartomeu also discussed Philippe Coutinho’s progress with the Blaugrana.
“I explained that we have a project with Dembele and Coutinho with Neymar’s money,” Bartomeu told TVE in Spain.
“Dembele’s level is better now than Neymar’s, he’s a much better player than Neymar and he’s already adapted.
“Coutinho is a great player, excellent, he’s getting better and better. It’s not easy to play at Barca – he was here six months last season and he’s complete now. He has the confidence of the coach. He’s a global player and we expect a lot. from him.
“He will continue at Barca. He’s different and Barca needs different players.”
With the 2018-19 season nearing its end, the 56-year-old also spoke of his club’s summer transfer dealings.
Barcelona have already signed Frenkie de Jong from Ajax for €75m (£64.7m/$84.8m) and Bartomeu didn’t rule out a return to the Dutch club for their defender Matthijs de Ligt.
He did, however, scotch persistent rumours linking Antoine Griezmann with a move to Camp Nou.
“The signing of De Jong we wanted to do in the summer, but there was a lot of pressure, other teams wanted him and we advanced it.
“With Ajax there is a very good relationship. With De Ligt , I do not know what will happen. It seems he will be on the market and when we talk to the coaches we will see if we’re in for him or not.
“His way of playing fits us and I like it. Ajax is a training club that sells, but we have not had talks.
“The Griezmann subject is not on the table.”
Bartomeu was asked about the prospect of facing either Pep Guardiola with Manchester City or Cristiano Ronaldo and Juventus in the upcoming rounds of the Champions League.
He said Barcelona fears nobody, and also reiterated his feeling Guardiola would return to the club he graced as player and manager.
“Cristiano or Guardiola in a final? Barca is not afraid of anyone, but we cannot speculate what will happen if we have not gone past the quarter-finals.
“Guardiola must return to Barca some day in the future, of course we would call him.
“He’s there at Manchester City and he is doing very well and has a very long contract.”
Barcelona hold a narrow 1-0 lead over Manchester United after the first leg of the Champions League quarter-final.
-Goal