Nice was in a word, unremarkable. I just didn't get what all the hype was about in Nice. Yes there was some shopping and the beach was decent, but there was just something missing. It was fairly crowded with tourists to see mediocre museums and a mediocre beach. There was also dog crap everywhere on the streets, one of the great charms of France. My favorite part of Nice was that they had a lot of Vietnamese restaurants and I couldn't get any good asian food in Spain. Obviously not a great selling point for visiting.
I based myself in Nice and visited Cannes one day and Monaco the next.
Cannes is better than Nice because it has sandy beaches as opposed to Nice's rocks. It also has 90% of the beaches reserved for public use by expensive hotels. That leaves a small portion of public beaches for the common folk while the old and rich and wrinkled lounge under sun shades.
Cannes is a quiet little town when I was there with the exception of the beach strip, so I would be curious to see what it would be like with the film festival.
Monaco I visited on the 3rd day and is much more interesting than Cannes or Nice. The town is more scenic as it is built into the side of the hills and there of course is the casino. I spent an entertaining hour watching the rich guys drive up to the valets in the casino with their outrageous Ferraris and Lamborghinis and expensive girlfriends.
There are also some pretty amazing yachts that you can see.
South of France for me was a big letdown. I still am not sure what all the fuss is about. I just want to get to Italy for some decent food.