The bad news is that Oldboy is a typical pointless American remake. The good news is that it's a decent one--not remarkable, but at least entertaining, particularly if you can keep yourself from constantly comparing it to the original. Which, let's face facts here, you're not going to be able to do.
Oldboy thoughtfully considers its twin themes of revenge and redemption, presenting dark comedy, stylized violence and emotional devastation. Not just good or great, it's one of the finest thrillers ever made.