300

And believe it or not, Blood Rayne.  While the story, acting, and plot all sucked major wuzits, the stages, locations, and costumes were all top notch.

perfume: the story of a murder is rather stunning in look and execution.

also perfect creature, although far from perfect, has a unique futuristic-retro look. but if your willing to watch blood rayne, you can get though this one...

krik

Easy Rider, "directed" by Dennis Hopper... the entire visual feel was created by the late Laszlo Kovacs. Kovacs won acclaim for his use of the scenery/landscape as an additional character in the film. The backdrop told the story as much as the "scripted" characters who were portrayed by actors. (Please excuse the emphasis quotes -- I just find it funny that this film won an Oscar nomination for a screenplay which did not exist, and Hopper receiving credits for directing this much-improvised film.)

Bound for Glory, directed by Hal Ashby, uses both Haskell Wexler's cinematography and very early use of the steadicam to great effectiveness, bringing a color vision which is both modern and reminiscent of Gregg Toland's work on The Grapes of Wrath (and any Toland film is worth considering in the answer to your request).

The Night of the Hunter, Charles Laughton's only film directed by him, was shot by Stanley Cortez. This film tells in shot after shot why it would not work in color, but black and white being the perfect medium for telling the story.

Here's a few most people miss:

1. Sky Captain and the World of Tomorrow
2. Dances With Wolves
3. Open Range
4. Gladiator
5. Pathfinder: Unrated
6. Sin City
7. Underworld
8. Underworld: Evolution
9. Flyboys
10. Apocalypto
11. Saving Private Ryan
12. We Were Soldiers

1, 5, and 6 were taken from graphic novels and the director's have tried to keep that flavor intact, though each approachs it from a different angle.  2 and 3 are examples of the use of scenery and attention to historical detail, and two of the best westerns ever put to film.  7 and 8 are both very dark and gothic in texture, but both are visually very stunning with superb CGI work.  9 uses a lot of CGI as well, but is very well done and has some of the best WWI flying footage ever put on film.  The only other WWI aircraft film that I would put up at that level is 'The Great Waldo Pepper' with Robert Redford where they filmed an actual dogfight with detail perfect full size replicas for the final scenes in that one.

A standout is 10.  Apocalypto is extremely violent, extremely bloody, but is superb story telling and graphically it will suck you in and not let go till the last frame.  Mel Gibson will become better known for his directing than for his acting before he's done.

Finally, 11 and 12 are visually stunning, very violent and bloody and emotionally disturbing to watch, but not gratuitous in the least.  They will show you what combat is like as closely as anyone will ever be able to put on film outside of actual combat footage.  Both are very high up on my list.

Every one of those I listed will be magnificent in high def, just as they are in standard DVD.

I'm looking forward to see how 'What Dreams May Come' turns out on hi-def.

Mirrormask
Elephant's Dream (its available on HD!)
Renaissance
Baraka
Blade Runner (cant wait for it in HD)
Brazil
Children of Men
Equilibrium
Immortel ad Vitam
Infrenal Affairs
Seven Swords
Natural CityPans Labyrinth
Secret Garden
Soundless
Suspiria
Twilight Samurai
Zatoichi

Many I thought of have already been mentioned, but here are a couple that spring to mind.

The Cell (2000) - For all the surreal sequences in the beginning and in the killers mind - the colour palette, detail in the sets, and just some of the strange imagery like the horse part   
Legend (1985) - The whole movie - For all the same reasons W0m6at mentioned Dark Crystal and Labyrinth, which this movie reminds me alot of in parts.

What Dreams May Come is gorgeous; I'm looking forward to the HD.
Manhattan (my favorite movie) - incredible NYC visuals