I'm not arguing, simply disagreeing with the OP's statement. Or expressing an alternative view, if you like. In case you didn't realize, I said she is entitled to her view, just that I disagree with some of it.
I climb many mountains and hills in HK, yes, some days you only see haze, but I've hiked and climb enough in HK to know there are also quite a few days when the air is reasonably clear and the view is terrific. To say all you see is smog every time you hike such that its not worth hiking at all is plain wrong. To say otherwise is frankly silly, in my opinion.
Hong Kong has many things against it too, but moving to Singapore, well, sure, you will gain some good things but also lose some other good points in HK.