This topic is the subject of much amusement in our family. I submit that if you are looking for quality Italian food you will not find any on Disney property. Many of the locations mentioned, however, are worthy if you seek a nice atmosphere. (I have not been to Palios so please exclude it from my comments)
Alfredo's is an example of the problems with many of the EPCOT restaurants. Alfredo's could, and should, be one of the finest Italian restaurants anywhere. Instead of a sampling of true Italian dishes Disney has chosen to "dumb down" the menu to satisfy the Chef Boyardee crowd. What a waste. To make matters worse the prices are exhorbitant. $15-$18 at lunch for pasta with cheese sauce?
Mama melrose's is simply awful though Portobello is eadible.
If the quality of food is your primary consideration, you are best served by driving up I-4 to Carrabbas. Though a chain, the offerings are superior to any Disney restaurant.