first of all. king kong is pretty much one of the worst films ever made. the writing was horrible the acting was horrible peter jackson's directing was good...but the rest was HORRIBLE.
second of all. no. these are not 'must see movies' these are simply movies that are entertaining. there is nothing wrong with pure entertainment purpose films...but they are not revolutionalizing, life-changing films.
to add to henry's list i will say solaris the original version, equilibrium, dirty pretty things, once upon a time in the west, and the cabinet of dr.caligari.
i cant think of more right now but thats because its almost 2am and i've been working all evening.