Argento is a fantastic director, don't get me wrong, I love his work. However, I think he is far from underrated. His work has been seen the world over, and appreciated outside of the horror genre.

Argento WAS probably one of the finest directors Italian horror had to offer, but since Opera his films have been severely lacking. The only decent one was Stendhal Syndrome, and that wasn't close to being on par with his output from '71-'87.

I would say Mario Bava is the greatest, and most cinematic of the Italian horror directors from the golden age of Italian horror. Argento has come close on occasion (Bird with the Crystal Plumage, Deep Red, Suspiria), but has still never surpassed Bava.