Flight Simulator movies are well-known videos among players on YouTube. Some show the player's ability to handle the aircraft in the worst situations, while others make videos to brag about their PCs' and how powerful they can handle this heavy game.
Here is a brief info about what you are going to need
Most of players use Fraps as a recorder, but feel free to use any other similar program. Keep in mind that you program must have the Full-HD recording option, as viewers will be more pleased with better video quality.
Lots of add-ons
As I said in the beginning, some players use the FS videos to show off. You don't want to post a video to brag about the default FS scenery, or its washed out textures. For that, I highly recommend third party applications which install high-resolution textures into FS and turn your game into piece of artwork , that you won't be able to distinguish your game from reality, such as REX.
Second part of add-ons are sceneries. There are several sceneries add-ons which you can find for free or for a small cost. Some alter the default sceneries, and some install whole cities.
Camera add-ons are also recommended, they allow you to take your videos from angles which are not available in FS at most cases.
Lastly, choose a good-looking aircraft. There are hundreds of free aircraft out there waiting to be flown with.
Now you know that you have to install graphics enhancement mods to make a better video, but the question is: Can your PC handle it?
It depends. You can either achieve 30+ frames per second by disabling most of the graphics options from the menu. Or you can have a realistic game by maxing out all the sliders in the price of frame rate. But the best result lies in-between performance and quality.
Video editing softwares
If you chose to sacrifice quality for best FPS, don't worry as you still can make an awesome, breathtaking video by choosing the right video editor.
You can apply exposure effects, bloom effects, change viewing angle and many more options.
Many good video editors are freeware, but the better ones are shareware. You can still make a good video from freewares such as the Windows movie maker which is a good starter
You can always fish out likes and subscribers by picking the right music for your video. Many videos I have seen were not as good as I expected, but with a great music, they reached high level of likes and views. So keep looking for the best soundtrack which suits you.
If you were to make a video about FS, you either make it right or you don't make it at all. If you can't fly an aircraft or land it, then you probably want to sharpen your skill, or else your video will be flamed by haters. Nobody wants to see an aircraft landing on houses, or crashing into another one!
Make it unique
If you want to attract viewers to your video, then make it about something new or least attended by other uploaders. Make it about a new itinerary, or to show a new add-on, for example. Because viewers are likely to view videos made by famous uploaders rather that going to your video.
Here is a video which I've made years a go in FS2004. As you can see it wasn't perfect as I was lacking the skills of video editing.
Here are links to useful softwares you might want to check
Fraps | Website
REX series for FS softwares | Website
Windows Live Movie Maker | Website
Sony Vegas Video editor | Website