Well, I enjoyed FS2002 then FS2004 (with force feedback joystick and some improved scenery as my only add-ons). I've since had some flying lessons (not many) and although of course it isn't particularly similar to real flying I found that I was more relaxed on my first flight as I had a better idea of what to expect.
Recently I've started using it to practice basic navigation (use of NDBs/ADF, DME and VORs). Again I'm aware that it's not the same - ADF needle doesn't point randomly every time you sneeze on the sim!)but it's kind of nice to be able to try out some of the theory from the comfort of your living room, and without actually killing yourself in thick fog.
I would like to bet that flying jets on the sim is nothing like flying real a/c.