holmen on 01 May 2017
I think emulation is good for past consoles. Not previous gen but really old stuff.
There are a few C64 games i really like but I do not have a working C64, tape unit, CRT etc and emulation is pretty much the only way to play those games.
As I see it, the biggest problem is usually dumping those old games from your tapes/cartridges/floppys etc. In many cases the media can no longer be read/dumped.
A newer example for me personally is the first xenogear. I cannot dump it from CD so I can play it on dolphin (it is not a huge problem since I have a Wii-U but if I could choose I would play it emulated in higher resolution)
As for most questions from OP I simply do not have data but I do not think emulation affect sales in a dramatic fashion.
Essay Pro