For a few years I've been working on making the 32-bit dead horse FSX flight sim come back to life. Microsoft mostly abandoned the business but it is still being carried by an active aftermarket community. There are the P3D and OrbX add-ons which turn the world into something acceptable and there are some gorgeous add-on cities such as from drzewiecki-design, but it is still a buggy and old engine at the core. It's like sticking a 427 in a Model T and trying to race competitively. There is only so much one can do before the stack of bandaids falls off.
So far I've converted this much over to photoscenery. The map coverages available are often bizarre. Retailers/creators will offer only half of a small island when it's just as easy to do the whole thing. Or detail up a single fence to max out the CPU but then ignore the rest of the more 3D objects. I am also working on getting FreeMeshX set up for correct and more detailed landscape horizons, but it is a manual process and many of the original airport heights have to be corrected one by one when elevated or sunk in the ground.
64-bit X-Plane is far better right out of the box, but it still creates an 'artificial' world.
I want to fly the 'real thing'.
Google Earth has an online flight sim which is incredibly realistic (created by all satellite data) but still with some glitches. Many internet connections like mine can't handle the huge amount of data transmission needed in real time and
AFAIK there is not really any aircraft dynamics or weather.
Now Microsoft is returning back to flight sims using Google Earth data and it looks like they might seriously nail it this time. MSFS 2020 is still in beta stages but looks promising: