I'm a western fan (John Wayne, Clint Eastwood, and others) and have noticed many areas of similarity between the game and movies I've seen. Here are a few:
- Once Upon a Time in the West - with Charles Bronson and Henry Fonda. The opening scene of the movie and many of the musical notes are almost exactly like areas in the game, most notably the railroad stations. There is even a harmonica that often plays like in the movie.
- Eldorado - John Wayne - there is one area that looks exactly like Monument Valley in which many westerns of the era were filmed.
- Rio Bravo - John Wayne - there is an area in the game with that name, and another movie Rio Lobo has a train that is much like what you see in the movie.
Much of the music is also reminiscent of the old Clint Eastwood movies (For a Few Dollar more, A Fistfull of Dollars, etc), and the Mexican villages are also very similar to what you see in the movie. In fact, I did a Clint-style gunfight with 5 Mexican bandidos which turned out just like it dies in the movie. ;D
For a fan of open world games, I can't recommend this one enough, especially if you're the type that likes more realistic play (as opposed to aliens, zombies, and the like)
Yeah it's very evident they pay tribute to a lot of western movies as GTAIV referenced a bunch of gangster movies as well. Additionally there's 3 titles you can unlock in MP called "The Good"/"The Bad/The Ugly" ;) Plus there's no better music to listen to while playing then the themes from westerns (specifically ones by Ennio Morricone).
If you take GTA Vice City for instance... it is absolutely like Scarface, you`d play as Al Pacino character, Tony (same name even, different surname).
Rockstar always finds a way to blend some movies references in their games, which they sure watched while developing the game and also helps in placing the player right into the game! :-X