The franchise is very popular here in the UK. Most people 25-50 regard Alien/Aliens as absolute classics, pinnacles of the genre - you don't meet many haters at all from that demographic. So many Brits in the cast and crew, the original trilogy was shot here etc. I'm not surprised at all, that it's doing very well over here. Obviously I say this with little/no knowledge of how the original films are regarded these days in the US/rest of the world.