All three have great cycling variety.
Food and wine is better in France and Italy, IMO. France marginally better for variety of food.
France is larger than Italy thus easier to wander before hitting water, has a larger road network.
I like France and would would recommend it, but love Italy, finding the people marginally nicer. I've been to Spain once, France 4 times, Italy 4 times.
West coast of Spain as well as Portugal would be the best choice if going to Spain.