genuine Best Film Ever contender

Rating: 10/10 (7 March 2015)

This is one of the few films that I have repeat-watched, probably about 5 times now. Saw it again last night after a 5-year gap or so. Still a rare 10-out-of-10. As ever, you must watch with the original audio so you get to appreciate the full range of the actors' performances.
Invariably with films where the plot's development is paramount you're also advised to stop reading even spoiler-free reviews...just go ahead and watch it.
If you are reading on, then I think the best advice for whether you'll like this film is if you have a strong stomach for dark psychology (and occasional graphic violence), and if you do, that you watch oldboy as if it's a pulp fiction comic (as in Breaking Bad, or indeed Pulp Fiction itself). The violence and story development is, at times, unrealistic, but this only makes the experience more beguiling as the character arc of the protagonist is so recognisably human.
Here's why oldboy deserves top marks and a steady place in those 'best film of all time' lists:

expert acting & dialogue weighted nicely with clever humour, giving the characters depth & relatability, with Oh Dae-su one of cinema's most memorable protagonists.

engrossing camera work & evocative music.

violence which is key to the plot, and fun/excruciating to watch!

perfectly-weighted story development and generally good pacing.

brutal yet unusual final showdown.

at least a dozen memorable scenes, you might have heard talk of a scene with a squid, but the scenes that stay with you forever happen later in the film when things finally get explained.

It's the very end, the actual final image, that struck the biggest chord with me. It's incredibly nuanced given what went on before...powerful, involving stuff...genuinely makes you think.
My other 10's as a guide to whether we have similar taste:
2001, There Will Be Blood, Excalibur, Apocalypse Now, 1984, Pink Floyd's The Wall