The original Korean and Spike Lee's remake are pretty much the same film with only a few slight differences. After a night of hard drinking a man gets kidnapped and is imprisoned in a hotel room for many years. Eventually the man decides to toughen up and seek revenge on whoever it is who has imprisoned him. Once he finally gets out he goes about doing just that.
Like I said, there are some slight differences in these two films but by and large they don't matter and each of the films stands on their own. They're both good meditations on vengeance and how it corrupts and fouls those who seek it. I recommend both. Spike's version is a little tighter and I like his ending better but the Korean version is over the top with and is stuffed with fantastical elements.
Turns out this sweet little film is also about vengeance but it shows you how to not let it overcome you. A young woman has a brief sexual encounter in 1950's Ireland and is forced into a convent to have her child. The nuns rip her child from her and give it to a wealthy American couple and she spends the next fifty years thinking about, loving, and secretly pining for that child. She meets a journalist who helps her find out what happened and along the way she figures out how to come to terms with it and how to forgive the unforgivable.
Coogan and Dench are terrific in this sweet film and I can't recommend it highly enough.