It's impossible to say which movie is your favourite one. There are so many choices. So here, I made a list you can copy paste and tell the community your favourite movies of all genres. Feel free to add more genres if I have missed something.

Action/Adventure:
Modern millitary/shooters:
World War II:
Horror: (Including psychological horror/shockers,splatters and everything around it. Unless you want to split it)
Comedies:
Action comedies:
Sci fi:
Zombies/infections:
Alien Invasion:
Drama:
Western:
Crimes: (Includes everything. From Homicides to Drug smuggling to Vandalism to Rapes and everything you liked. )
Animated:
Series: (E.G: Resident Evil, Star Wars, Fast and Furius, and in general, movies with more than 3 sequels or prequels)


And which one would you pick out of the ones you already picked?

These are mine.

Action/Adventure: V for Vendetta.
Modern millitary/shooters: Executive Decision.
World War II: Saving Private Ryan.
Horror: {Splatter= Hostel 1} {Psychological= La piel que habito} {Sci fi= Silent Hill: Revelations}
Comedies: American Pie 3
Action comedies: The losers
Sci fi: Star Wars Episode III
Zombies/infections: World War Z I guess.
Alien Invasion: Battle Los Angeles.
Animated: Robots.
Drama: Dogtooth (O Kynodontas in Greek.)
Western:The good, the bad and the ugly.
Crimes: BLOW.
Series: Star Wars.

Favourite of all these: Executive Decision. Really tough choice.