It changes, right now my personal favorite ones are:
1. Fight Club (David Fincher)
2. The Matrix (The Wachowski brothers)
3. RoboCop (Paul Verhoeven)
4. Terminator 2 (James Cameron)
5. The Dark Knight (Christopher Nolan)
6. The Empire Strikes Back (Irvin Kershner)
7. The Great Gatsby (Baz Luhrmann)
8. The Truman Show (Andrew Niccol writing)
9. There's Something About Mary (The Farrelly Brothers)
10. 300 (Zack Snyder)
Zack Snyder is very underrated because he is mainstream, Man Of Steel was a fantastic movie for example, you just need to be into that kind of stuff to appreciate it.
I also love movies like Rush by Ron Howard and stuff like Roma or Gravity by Alfonso Quaron.
Andrew Niccol is my favorite screen writer, so I also like movies like In Time.

Critically my favorite movies are:
1. The Kid 1921 (Chaplin)
2. Wuthering Heights 1939 (the same guy that made Ben-Hur)
3. Bambi 1942 (bunch of cool artists)
4. The Ten Commandments 1956 (founder of Hollywood)
6. 2001 A Space Odyssey 1968 (Standley Kubrick)
7. American Graffiti 1971 (George Lucas)
8. Blade Runner 1982 (Ridley Scott)
9. Basic Instinct 1992 (same guy that did RoboCop)
10. Catch Me If You Can 2004 (Stephen Spielberg)
Obviously the Back To The Future movies by Robert Zemeckis are great, The Dollar's Trilogy by Sergio Leone, and The Godfather movies by Francis Coppola.
Honestly if you show me any movie by any of all those guys mentioned, chances are I'm going to like them all.