If I had to pick a movie or movie series for best of all time, I would say The Lord of the Rings trilogy.
IMO the sheer magnitude of work that went into as far as production, music, cinematography, imagination, and story, its hard to beat.
Tremendous attention to detail and realism, fantastic battle scenes (Helms Deep, and later the Battle of Minas Tirith) that realy got the heart pounding. If they didn't make you want to grab a sword and go kill some orcs and Uruk 'Hai...
When Faramir and his mounted unit charge to their death on the orders of Denethor, and all you here is the song....man, what a sad part.
Yeah, I love The Godfather movies (I even like Pt III), and there are many great movies...but I stick with LOTR trilogy (extended versions) as the greatest movie making masterpiece ever made, possibly ever to be made.....