The Frenchman has come under fire numerous times after failing to live up to the £30m fee that Spurs paid for his signature from Newcastle United in 2016.
So far this season, Tottenham manager Mauricio Pochettino has started Sissoko in 12 Premier League games and has brought him on as a substitute in a further 14.
In an interview with Goal.com, Firmino listed the obvious standout talents in England's top flight, and included the Tottenham midfielder.
"We have great players in English football, it's hard to select one as the outright best," said the Brazilian. "That's why it's the most popular league with many quality teams. We can talk about the goalscorers [Mohamed] Salah and Harry Kane.
"We also have Gabriel Jesus, Kevin De Bruyne and Ilkay Gundogan in Manchester City, Paul Pogba and Romelu Lukaku at Manchester United, Moussa Sissoko and Mousa Dembele at Tottenham, Willian and Eden Hazard at Chelsea, Mesut Ozil at Arsenal.
"Not to mention [Sadio] Mane, Emre Can, Dejan Lovren and the many other good players we have here at Liverpool. It is a league with great stars. Virtually everyone I mentioned will be at the World Cup. The level is very high."
Firmino has scored 23 goals in all competitions this season and has created 10 assists.