I am a huge fan of retro and indie games and you are correct in saying that emulation keeps things alive.
Most games old school games have moved to mobile, prime example is the SNK games. If it was not for emulation I would not be playing comix zone again.
We also have different expectations from emulated games in comparasion to new games.
It could range from difficulty,gameplay, gaming physics and explansions ..
Also emulation keeps the nostalgia alive. Which is why I still play The legend of dragoon a PS1 title that we are now able to play on later Playstations.