In a way I am cheating..because I saw the American reworked version first and it was awesome. I am definitely NOT an overall foreign movie buff. But, I am sure you agree since u asked, the U.S. does NOT corner the market in talent hehe 8)
The Departed---Jack Nicholson, Matt Damon, Mark Wahlberg and quite a few other famous folks.
It is a remake of a fantastic Hong Kong movie called "Infernal Affairs", it starred Andy Lau and Tony Leung.
The story theme and essence is basically the same....but the details are geographically and culturally, quite different.
From my perspective, I would suggest watching the Chinese film first. Personally, I watched em the other way around and I think the American way of "going over the top ...shock and awe" way of entertainment kinda took away a little bit of how well written, filmed, and acted the original was.
I have to say tho, The Departed kicked butt!!!I have enjoyed every movie with them 3 Actors in it.