When I went last week to a meeting in Cannes, I checked the board for any recommendations, but could only find unanswered requests. Thus, my wife and I roamed this nice resort for three days looking for acceptable food (regarding price and quality), and this is what we (and the concierge of our hotel) can recommend:
1. Seafood: Astoux et Brun. There is a row of seafood places on Ave Felix Faure, but the busiest and maybe best is Astoux et Brun. No reservations possible, you have to wait in queue if you arrive after 7:30 p.m.. The freshest and best seafood, and a very fast service also. The ambiente is that of a busy fish market, so dress casually.
2. French, Provencial and Italian: 3 Portes. This very cosy restaurant is located in a backstreet of the Croisette. It offers excellent and inventive French, Provencial and Italian cuisine and remarkable low prices. They even have a website (in French). I had a great pate from duck liver and rabbit, and a wonderful risotto with squid prepared in a whole loaf of parmigiano. The desserts using chocolate were also remarkable, as well as the local wines.