Ok, no one has yet mentioned Truffaut (either that or I just didn't read the previous posts clearly). 

Try, Jules et Jim - Truffaut's best film and one of the finest romantic films ecer made.

Stollen Kisses/Bed and Board - It's not necissary for you to have seen The 400 Blows in order to enjoy these films.

The Last Metro - Less enteresting than the others but equaly enjoyable...well maybe.