There are many good flight simulators some good some bad. I like RFS and Infinite flight and simple planes they are cheap and can run on any device.
I will compare all the flight simulators one by one
by the scenery, aircraft, airports, simulation, and variety

Scenery

Infinite flight
As you all know it has the dumbest scenery
But they look good from a height.

Simpleplanes
It has good scenery but not the best
there are mods available to make them stunning.

X plane mobile
X planes scenery is bearable to look at. they are much better than infinite flight.

Aerofly FS 2021

it has the best scenery as of my thoughts.it has 3d buildings also.

RFS

it has good but not the best scenery and 3d buildings also

so Aerofly wins this round

Aircraft

As you all must be knowing infinite flight has the best Aircraft models sound and the textures are detailed also.

X plane

X plane has some sort of toy-like aircraft

Simpleplanes

It depends on how you make it!

Aerofly has a good texture shadow and many but not the best