For me, it has to be “Old Boy” which is originally a Korean movie but the US version sucks so much that it remains incomparable. Another contender is “The Ring” again a Japanese movie (the ending differs between both versions, as the original one refers to the protagonist’s father sacrificing himself but the remake states that the cursed tape is being sent to someone else, passing the omen towards another stranger).
I enjoyed Utopia, and would have liked to see what else they had in store.
I think I got halfway through the first season of the British version, but not for anything the show did. I just kind of ran out of steam.