Dear lord, you want this limited to five? There are sooo many good movies out there. MY list may get very artsy fartsy so I apologize in advance.
Well I'll start with one of the movies I saw when I was still a kid:
Mad Max (1 and 2) this was of course Gibson became a total tard. I allways remember things from this movie. Also I love apocalyptic themes and stuff like that so it really was the perfect movie for me. (if anyone chooses to rent this makesure not to get the dubbed version, yes they dubbed out the 'Austrailian' and put in 'english' instead)
Sin City. Holy hell this is a good movie, on nearly every level. Definitly opened up the realm of what could be done with movies.
Akira Kurosawa (Director) - All his stuff is excellent, if I had to pick one movie it would be either Yojimbo, or Ran... or Seven Samurai. He really was prime film maker, master class.
The Seventh Seal by Ingmar Bergman, one of the best movies I've ever seen. Ever. I havn't seen any of his other stuff, I wonder if it even approches the mastery that is The Seventh Seal.
The Professional. That's the name I saw it under anyways, its also called Leon. This is my favorite all time movie ever. I saw it when I was like 14 -16 and totally fell in love with it (and Natalie Portman

). I think it is movie perfection embodied (her too

).
Of course with such a limited list you leave out so many important others, like Zhang Yimou's films, certain Korean films (
Oldboy, or War Kong Wai), or more Japanese films (Beat Takashi, Miike), or even single films like
Requim for a Dream (super powerful movie) or
Natural Born Killers. Least of all Tarintino who is definitly an important figure in modern film (although I felt it was safe to assume he would get the credit he deserves anyways). Hell I could do a list of just awsome Canadain film that would be well over 10 seminal works.
Edit - Oh yeah I thought I'd include a list of my favorite Critics: Ebert... Thats it. Even if I dont allways agree with him he is always worth reading, his points are well writen and thoughtful and most of all, the dude totally loves films (whereas I get the impression most other critics come to hate them or don't care). His rating sytem is totally skewed though, only films with a four rateing or a one rateing are sure things the rest is nonsense.