In the British Isles it has always been celebrated, having it's roots in the Celtic festival of Samhain, the festival probably pre-dates the Roman Invasion, which could make it one of the worlds oldest continually celebrated traditions. The America's seem to particularity like it, and that has led to the celebration being exported to nations which don't have a Celtic history.
I celebrate it, it's also damn convenient that Bonfire Night's on the 5th November, so quite often you'll have a Halloween party and then a Bonfire Night party in the same week. Then you have Christmas to prepare for... busy part of the year Winter.