UK's Channel 4 has compiled a number of 100 Greatest Lists, including this ranked list of "The 100 Greatest Films of All Time" at Filmfour.com.
Descriptions are from their site. Full reviews of each film may be found there.

Facts and Commentary About The List:

• The ranked list represents a wide range of some of the most innovative, popular and striking films across all major genres, with special consideration of their appeal and significance to a modern British audience.
  
• The list aimed to include films that are generally considered as classics of cinema, broke new ground in technique, subject matter or ideas, had phenomenal popular appeal and a lasting impact on popular culture and represent the greatest work of cinema's most respected directors and performers.

1. STAR WARS (1977), STAR WARS EPISODE V: THE EMPIRE STRIKES BACK (1980)
Unable to procure the rights to Flash Gordon, George Lucas serves up his own homage to the Saturday-morning adventure serials he loved as a kid; somehow managing to create possibly the most revered and successful film series ever in the process.

2. THE GODFATHER (1972), THE GODFATHER PART II (1974)
Coppola's epic, operatic, bullet-ridden saga of a Mafia family at war with itself and its rivals. Murder, betrayal, ambition: it's all here, and utterly compelling, with Brando at his scene-stealing best.

3. THE SHAWSHANK REDEMPTION (1994)
Mugged at the Oscars by Forrest Gump, this irresistible prison drama promotes the unquenchable human spirit with an intelligence that the gooey Gump readily sacrificed.

4. PULP FICTION (1994)
Tarantino, the boy wonder pushed his storytelling powers to their limits to make this film every bit as BIG as the widescreen 70s hits that inspired him. An instant classic.

5. SOME LIKE IT HOT (1959)
Wilder and Diamond's script crackles with ideas and gags, and the performances are uniformly assured, with Curtis's triple characterization in particular a revelation. Monroe was reputedly at her worst on set, fluffing take after take, but whatever was necessary to achieve this brilliantly sustained gem was worth it.

6. GLADIATOR (2000)
Ridley Scott revives the Roman epic with computer generated imagery and a mighty performance from Russell Crowe. Not to mention the last stand of the late Oliver Reed.

7. IT'S A WONDERFUL LIFE (1946)
Capra's Christmas perennial is a lot darker than its status as prime festive schedule-filler would suggest. That's not to say it will have you hiding behind the sofa but, for a film that deals with missed opportunities and one man's dark night of the soul, it is all the more impressive it has garnered a feel-good reputation.

8. BLADE RUNNER (1982)
Dystopian thriller Blade Runner remains the most influential sci-fi masterpiece of modern cinema, notably for its immaculate visualisations of retro-futuristic urban decay.

9. SCHINDLER'S LIST (1993)
A heart-rending and redemptive Holocaust story, this Oscar-grabbing epic added to Spielberg's directorial credibility, showing he could handle controversial, sophisticated stories with real sensitivity.

10. GOODFELLAS (1990)
"As far back as I can remember, I've always wanted to be a gangster," Henry Hill opens his true story of 30 years in the mob in Scorsese's epic.

11. PSYCHO (1960)
The music, the setting, the shower scene, the mother in the cellar... everything about this iconic film has passed into cinema history. A genuine virtuoso classic and the grandaddy of all slashers.

12. JAWS (1975)
It left a generation of schoolkids afraid to go into a swimming pool, let alone back into the water. Wunderkind Spielberg's story is all the scarier for hardly ever showing the Great White that is most of the characters' nemesis.

13. APOCALYPSE NOW (1979)
Martin Sheen journeys through Vietnam and Cambodia to terminate flipped-out renegade US colonel Marlon Brando. But his mission becomes a screaming trip into madness, stunningly realised by Coppola's hallucinogenic direction and a cast dragged from Hollywood's Narcotics Anonymous.

14. ONE FLEW OVER THE CUCKOO'S NEST (1975)
Jack Nicholson excels in this multi-Oscar winning, anti-authoritarian tale, the last of the great counter-culture Hollywood movies.

15. THE MATRIX (1999)
The Wachowski brothers' ground breaking, morphing and shattering sci-fi spectacular. Featuring Keanu Reeves and kung fu like you've never seen it before.

16. CASABLANCA (1942)
With nearly every line of its script engraved on the collective subconscious, and its central performances of Bogart and Bergman defining iconic cool, Casablanca is an exultant classic. "Here's looking at you, kid".

17. THE USUAL SUSPECTS (1995)
One of the outstanding thrillers of the 90s boasts a screenplay that is both bewildering and utterly, brilliantly logical. A film that immediately makes you question what you have just seen and whether it can really have been as good as you think.

18. CROUCHING TIGER, HIDDEN DRAGON (2000)
A highpoint of martial arts cinema from Ang Lee no less, which blends the latest fight effects into a 19th century China epic of love and valour. Swashbuckling on the grandest of scales, with Chow Yun-Fat and Michelle Yeoh.

19. CITIZEN KANE (1941)
The world's most acclaimed film, too often on the top ten lists with critics flexing their reflexes rather than their minds. Even so, it is mesmerising and the young Welles threw down a challenge to Hollywood from which neither fully recovered. A masterpiece.

20. RAGING BULL (1980)
A genuine moment of cinematic genius. The physical and emotional punches come so thick and fast, you have to check yourself for bruises.

21. ET: THE EXTRA-TERRESTRIAL (1982)
Before the likes of Independence Day and Evolution, there was a time when movie aliens were cute and nice and only wanted to be our friends. Essential Spielberg.

22. TAXI DRIVER (1976)
Stone-cold classic. Robert De Niro is electrifying as the Vietnam-scarred taxi driver with a frightening take on the justice system.

23. LIFE OF BRIAN (1979)
History is rewritten and sacred cows are merrily sacrificed as the Python team unleash their alternative take on certain well-known events from 2,000 years ago.

24. SINGIN' IN THE RAIN (1952)
Gloriously exuberant and abidingly popular musical from the 1950s heyday. Stanley Donen's film sets the Gene Kelly/Debbie Reynolds romance against the fascinating backdrop of the coming of sound in movies.

25. LA CONFIDENTIAL (1997)
Brilliant adaptation of James Ellroy's detective novel about three cops facing corrupt businessmen, sleazy journalists and assorted trash in 50s LA.