I think the question of will they look good is subjective. They will look like older games blown up, so will look "rougher" than you probably imagine. There are lots of things you can do to change the look though some may frown on this, I like having these options. If you are using say Retroarch, there are lots of options with shaders to change the look, you can for example emulate the games displaying on a CRT TV which will make them look more authentic.
This is probably a whole subject, so worth searching through to find some ideas of Retroarch and the settings you can tweak.
Here are a few examples of different looks you might apply.