For photosceneries, there are also the nice Blue Sky Scenery tiles for several US states. There is no autogen or night textures, but nonethless they are of high quality. Best thing is they are donationware, so you can download them for free and you decide how to support the devs. There are kazillions of options to choose, if you just focus on the smaller areas and not even try to improve whole globe. I have huge amount of different sceneries from Aerosoft Antarctica to PacSim islands and from ORBX to MegasceneryX photoreals (SoCal is by the way incredible!).
If you are looking generic world wide improvement, things narrow down tremendously. There are, as you know the GEX-packages, which improve pretty large areas. I used GEXNA with FSX but ditched it when I transferred to Prepar3D. There are FScene Packs, which I own, but they are sort of a mixed bag and I don't use them. Best general improvement so far are Leclercq's freeware season packs added with his 30cm/50cm projects. I have those installed with Cloud9 landclass and FSGenesis mesh where available and I'm completely satisfied with the results in the areas, which are not part of any specific high detail scenery packs. Also, using just good landlclass and mesh can improve the overall look of the scenery tremendously.