Lord of the Rings, although I tend to get uber-addicted to one thing at a time, and LotR's is it right now, hell, sometime last year it would've been the original Star Wars trilogy.
I've never actually watched Back to the Future, details..?
I love LotR quotes..^_^
"I am a servant of the secret flame of Arnor. The Dark Fire shall not avail you, Flame of Udun!
Go back to the Shadow. YOU SHALL NOT PASS!" - Gandalf the Grey, Bridge of Khazad-dum
"Is this it? Is this all you can conjure Saruman..?" - Theoden, Battle of Helms Deep
A: "I do not know what strength is in my blood, but I swear to you I will not let the White City fall, nor our people fail."
B: "Our people, our people. I would have would have followed you, my brother... my captain... my king.
A: "...Be at peace, Son of Gondor. - Aragorn and Boromir, after the Battle of Amon Hen
"There is only one Lord of the Ring, only one who can bend it to his will. And he does not share power." - Gandalf the Grey, to Saruman
"This is no mine. It's a tomb." - Boromir, when entering Moria
"Moria... You fear to go into those mines. The dwarves delved too greedily and too deep. You know what they awoke in the darkness of Khazad-dum... shadow and flame" - Saruman the White, about Gandalf
" I would have gone with you to the end, into the very fires of Mordor." - Aragorn, to Frodo shortly before the battle of Amon Hen
"One does not simply walk into Mordor. Its black gates are guarded by more than just orcs. There is evil there that does not sleep, and the Great Eye is ever watchful. It is a barren wasteland, riddled with fire and ash and dust, the very air you breathe is a poisonous fume. Not with ten thousand men could you do this. It is folly." - Boromir, at the Council of Elrond
"My business is with Isengard tonight, with a rock and stone. Rarum-rum! Come, my friends. The ents are going to war. It is likely that we go to our doom: The last march of the ents!" - Treebeard, before marching to Isengard
"Spears shall be shaken, shields shall be splintered. It is a sword-day; a red day, ere the sun rises! Ride now! Ride now! Ride for ruin, and the world's ending! Forth Eorlingas!" - King Theoden, before Rohan marches to the Pelennor Fields
"Men of Gondor and Rohan, my brothers! I see in your eyes the same fear that would take the heart of me. A day may come when the courage of Men fails... when we forsake our friends, and break all bonds of fellowship... but it is not this day. An hour of wolves and shattered shields when all hope comes crashing down, but it is NOT this day! This day, we fight! For all that you hold dear, stand, Men of the West! " - Aragorn, before the Battle of the Black Gates
"My preciouss..." - Gollum, numerous times
"I have not passed through fire and death to bandy crooked words with a witless worm!" - Gandalf the White, to Wormtongue
"Now for wrath, now for ruin, and the red dawn!" - King Theoden, before Rohan rides out of the Keep of Helms Deep
"Ride out... ride out and meet them..."
"For death and glory"
"For Rohan. For your people" - Aragorn and Theoden, inside the Keep of Helms Deep
"The Horn of Helm Hammerhand shall sound in the deep, one last time!" - King Theoden, inside the Keep of Helms Deep
"Theoden King stands alone"
"Not alone. Rohirrim! To the King!" - Gandalf and Eomer, near the end of the final battle of Helm's Deep
I would have to say the X-Men Trilogy would have to be the best since it actually follows the original comic and cartoon story line. I would have to say the Matrix would have to come in second, that was just awesome all around.
The original Star Wars Trilogy hands down. No other series of movies has ever captured my imagination like they have. I also give a nod to the Indiana Jones Trilogy (I am pretending that the new one isn't being made after I heard that Lucas wants to make Indy's whip CGI.)