I think Our midfield has more depth than any team in Serie A. In terms of quality, we're not very far from the top. Juve, especially recently, have really improved in the middle. Aquilani is beginning to exhibit some top class quality. Melo is developing into a star man for our side. Marchisio is steadily finding his place in the team. Sissoko is great but just can't find a spot in this starting 11. And I think that's how you know how much we've improved this season.
It wasn't a long time ago when the absence of Sissoko meant disaster for Juve. Our midfield was completely lost without him. Now, we've significantly improved. In fact, our center midfield is so good that Del Neri would prefer playing an extra CM out wide(Marchisio).
I'm going to try my best to show how much we evolved in the last 3 years in that department.
I think it was Almiron Tiago Marchisio Poulsen Sissoko -> Melo Marchisio Sissoko Poulsen -> Aquilani Melo Sissoko Marchisio.
Compare that to Roma's Pizarro De Rossi Brighi Taddei.
Or Milan's Gatusso Pirlo Flamini Boateng.
Or Inter's Cambiasso Stankovic Muntari Motta.
Personally, I think if Melo continues growing with every game. And Aquilani stays fit and regains his old form, Momo regains match fitness, and Marchisio stays consistent. I'd say we would easily have the best midfield in serie A.