I assume you're refering to desktop simulators like FS98 (or FS 2000) but more realistic in terms of systems that are simulated. There's a new sim out called Fly!. It's a new program that is said to be the best so far in "normal" desktop sims. Haven't tried it my self yet so can't really comment. There's a commercial add on for this flight sim for the 757.
Follow these links:
Fly! homepage
http://www.iflytri.com/
and for the add-on
http://www.precisionmanuals.com/
Cosmo