Carmen is a great opera. I like Stravinky's Opedipus Rex (with libretto by Cocteau) a great deal. It's incredibly powerful stuff. The version I saw which was staged by Julie Taymore was AWESOME! Her work is so inspired!
boheme of course.. if u can't love boheme then there isn't the slightest ounce of compassion/romance within you. anything by puccini is always good. verdi of course. no wagner though!
My favorite all time Opera is - Rigoletto by Giuseppe Verdi. Anything by Rossini, Puchini, Verdi and Wolfgang Amadeus Mozart is GREAT! Here is my Top 10 Operas of all time. These are all VERY MOVING and VERY BEAUTIFUL, enjoy! Rigoletto Barber of Seville La Boheme La Nozze di Figaro (The Marriage of Figaro) DIE ZAUBERFLOTE (The Magic Flute) Don Giovanni Tosca La Traviata Carmen Madam Butterfly