What Equipment do I need?

While it is possible to use most flight simulators with a mouse and keyboard the minimum equipment should be a joystick. These can be obtained at little cost and enhance the flying immensely and is expected of all flight simulator manufacturers.

Can a desktop simulator be used for real world training?

Flight Simulators have been a part of pilot training since there have been human powered flights, so with this pedigree then we have to say YES!

Using a flight simulator can help you with the basics of flight, what the control surfaces do, what the basic instruments are for, etc.  It can also help you when it comes to practising flight procedures such as instrument approaches and with decent photo scenery installed visual approaches to unfamiliar airfields.  If you are training to become a pilot ask your flying instructor for how best you might use a flight sim to improve your real-life flying.

Which is the best flight simulator to use?

The difficult ones first, eh?  It's a bit like asking which is the best car... It depends what you want to do.

The most popular flight simulator by sheer volume has to be Microsoft's Flight Simulator (FSX) which has been around for so many years. [https://fsxinsider.com/] The number of add-ons which have been produced commercially or available from the flight simulator community free of charge is vast. Then there is P3D, or 'Prepar3d' from Lockheed Martin who have built on FSX and improved it.

More...