I almost burst out laughing at this!
Most cinemas these days are digital 4K, before that most were 35mm film which a few special cinemas that could handle 70mm
Stick a DVD on and project it at a 50ft wide screen and see how bad that would be, even 1080p would look quite soft (I've seen this done a couple of times and although it wasn't bad it wasn't great either)
Firstly I don't think any cinemas anywhere near here are 4K yet (they would be shouting about it if they were), secondly just because its a certain resolution doesn't make it "HD" when its outputted via a projector (in the same way that a 4K film running full screen on a 22" 1280*1024 CRT wouldn't be 4K) the end result is that the average cinema looks nowhere near as good as a Blu Ray (hell most new films on DVD look better, especially upscaled).





