After Season 1 of the US version, I would say the British version is easily better. But I was one who liked the US version from the beginning, even though if the show had kept the tone of Season 1, it would never have become a big hit. Ironically, Season 1 is when the US Office was most trying to borrow the tone of the British version.

Season 2 of the US version was probably its best, and almost every episode knocks it out of the park. The US characters came into their own as separate people from the British versions, the supporting cast became real, and the US version really found its own voice. By the end of Season 2, I would have easily said that the US version was superior, just because there could be 20 episodes a year of such wonderful and hilarious television.

Season 3, in my opinion, was great, even if it didn't match the perfection of Season 2. They found ways to expand the world of the show, to flip the Jim/Pam dynamic around while still keeping it interesting, to bring in new characters, etc. I would still be comfortable calling the show better than, or as good as, the British version at this point. Season 4 had several outstanding episodes, but now we have come full circle to the point where I would call the US show good, even great, but not as good as the original. The British version will always be its own self-contained world of 12 episodes plus a special, and there is a certain perfection and completeness in that (plus you can sit down and watch the whole thing on a rainy Sunday). I am a little disturbed at how broad the US version is now getting, relying too much on slapstick and unbelievable situations. Yeah yeah yeah, even my precious Season 2 had some episodes that were like that (Michael burning his foot on the George Foreman grill, Michael and Dwight's fight, etc). But where in Season 2 the over-the-top elements were the exception, it seems like in Season 4 they are becoming more and more the rule, and it's harder and harder to believe that we're actually watching real people in the real world. I still love the show, and will still keep watching it, but, my god, I popped the Season 2 DVDs in the other day, and I had forgotten how good the show actually was back then.