Well, having never flown anything other than off the handle or into a rage, I've no idea how realisticly any of these aircraft are modeled. But some payware do nicely model systems and engine management; the Digital Aviation Do-27 (http://www.flight1.com/products.asp?product=DO-27) is one of my favorites, the engine shudders if the throttle is advanced too rapidly, it can overheat, you even have to add oil periodically ...ignore maintenance or proper operation and you may find yourself at 5000ft with a dead engine (I've made a few landings with a "sick" engine). Freeware aircraft vary greatly, some seem to have gauges almost randomly tossed in, so your engine may appear to never warm up, or oil pressure is ludicrously high, during normal operation.
But, as KCD mentioned, all simulators, whether flight, racing, or other, lack any kinetic feedback - you don't have the feel of movement, only visual and audible input. I've long argued this aspect of racing sims; I was very much a "seat of the pants" driver so am quite mediocre driving on a screen. I wonder if real pilots have the same issue with flight sims.