Sansho the Bailiff,Seven Samurai are accessible and truly great masterpieces which should be an excellent starting point.La Regle du Jeu,Battleship Potemkin,L'Atalante,The Passion of Joan of Arc,Tokyo Story,8 1/2,Apu Trilogy, Andrei Rublev, Persona are all(rightly) highly rated by  international critics but some are more accessible/easy to appreciate than others!
 I love The Green Ray and Alice in the Cities, but that's probably more personal.Eternity and a Day also, but it's certainly not for all tastes(may be too slow for most).Renoir's Partie de Campagne is a lovely short (about 3/4 hour);try it if you fancy a lyrical French Summer riverside outing and/or like his father's paintings.Of recent popular successes,i enjoyed Crouching Tiger Hidden Dragon, Cinema Paradiso was o.k, but i'm sorry to say i didn't like Amelie(too sweet for my taste) or Life is Beautiful,though most others seem to have loved them.Jean de Florette has popular appeal, is a fine film.Babette's Feast for something Christmasy and uplifting.The White Balloon is charming.For a  sci-fi silent, try Metropolis,sheer genius.Aguirre Wrath of God for a  tremendous Conquistador adventure in Peru. I hope this doesn't confuse you, when compared to the suggestions from others.Many in the ForeignFilms'100 (poll) i've not mentioned are also well worth checking out.Anyway, Nadolig Llawen a Blwyddyn Newydd Dda,(Merry Xmas and Happy New Year) as we say in Wales.