I must confess that I have only heard Les Mis and Miss Saigon. DO they have more shows? Has anyone heard them? It seems impossible that their oeuvre could be so small.
Revolution Francaise was their first show (well concept album like the French Les Miz, but like that it was later staged), but I believe some of the score is by another writing team...
Otherwise, off the top of my head, Les Miz, Miss Saigon, Martin Guerre and Pirate Queen. Shoenberg has also done some ballets (one based on Wuthering Heights), and Boubil and Shoenberg, kinda oddly, worked on the musical Marguerite together but the actual music is by Michel Legrand, and like with Miz, Kretzmer translated Boubil's lyrics to English where it ran in London--I don't believe it ever even had a French production.