Having never flown a heavy jet or a Heavy simulator My knowledge in that area is limited however I can say based on the simulator and flying experience that I do have Frasca sim and private licence, IFR student that the PC flight sims are of no use whatsoever. The only thing I find FS2000 useful for is to figure out how to enter holding patterns and figure out navigating by instruments, It is instructive to "fly" the route on the sim before you fly it for real so that you know what to expect in terms of navigation, communication and approaches e.t.c. It teaches you nothing of the stick and rudder skills required. The Frasca is a little better but although it is an approved training device it still gives you nothing in terms of feedback. You could not learn how to fly like those murderous bastards did by just using a PC.
Friends of mine who work for airlines tell me that their first time in a heavy jet sim they fly very badly and only get a feel for the big guys after a few hours of training.