Been French and back in France for the last 14 years, I guess I am terribly biased. After tasting so many different melons, I have found that I always go back to the Charentais melon sometimes called melon de Cavaillon. To me, it is one of the best, but then, there is no accounting for taste. For instance, I really detest watermelon.
It is a small, bright orange, sweet, juicy and perfumed cantaloupe type melon. When really sun-riped, the sweet smell assaults your nostrils before you've had a chance to put a morsel into your mouth. It is delicious and almost melts in your mouth. Of course, it has to be really ripe otherwise, you just have a lump of melon flavoured, hard, watery, coarse textured...thing! Well, you can see I'm biased!
Wikipedia says:
It is a small variety of melon, around the size of a softball. It has flesh similar to most cantaloupes, but with a distinct and more intense aroma, and a more pink hue. It originated in the Charentes region of France, and is most associated with the Provençal area around the town of Cavaillon. Most true Charentais melons are grown in and around this region, and are almost exclusively available in France, owing to the fact that their thin skin and soft flesh does not do well in shipping. Hybrids of this variety are widely grown, they are generally crosses with North American cantaloupes for better shipping characteristics and larger size.