It won stuff at Cannes, is tremendously over the top and violent and yet the film that Oldboy reminded me of the most was Amélie. Not just because it employs a visual toolbox which encompasses state of the art digital trickery along with some wonderfully choreographed camerawork. But that the film drifts in and out of the conscious thoughts of our lead Oh-Dae-Su, often picking up his hallucinations, flights of fancies and torture along the way.
Also like Amélie this is at its heart an unlikely romance. What with the films revenge film trappings the romance seems hugely out of place (which is why I managed to guess its significance). That said it is a cute counterpoint to the driven lead.
Oldboy is a frequently ludicrous thriller whose overall audaciousness married with some knife-edge acting makes it thoroughly enjoyable. If you like films where people eat octopuses whole, giant ants ride the subway and people get their teeth pulled out with a claw hammer. I might suggest therefore that if any of those things put you ill at ease, then Oldboy might not be for you. It certainly lacked the focus (and no nonsense title) of the same directors previous Sympathy For Mr Vengeance. What it loses in pathos, it gains in entertainment. But it is in its heart just a a violent Korean version of Amélie.