Le Souffle is my favourite film ever - I could watch it at any time and in any mood. Lacombe Lucien is stunning, as is Au Revoir les Enfants. These would be my Malle top three. I love Atlantic City too, and I can understand why Les Amants was so important. As for My Dinner with Andre, I watched it once and quite enjoyed it, but I'm not sure I could do it again. I have tried to watch Le Feu Follet on several occasions, but haven't reached the end yet - I'm sure it's worth it, but it's so heavygoing!
For me, Malle's work with child actors marks him out from the rest - only a few (Truffaut, maybe Spielberg, Bergman in Fanny and Alexander) can match him. In Le Souffle Au Coeur and Au Revoir les Enfants in particular the casting is faultless.