The only problem with most of these suggestions is that they involve vehicles which are, compared to your average airliner, relatively easy to drive.
This means that you're not going to have the same effect that F$ has. There are no landings in a Corvette, no altitude changes in a boat. About the only thing I can think of that might be even remotely challenging is perhaps a cruise ship, but even that moves at such ridiculously slow speeds that I can't think it would be an exciting game.
F$ got its reputation as a sim for being challenging, and being something very complex. You can't compare having to know flap settings, AP settings, airspeed laws, airspace restrictions, trim wheels, engine gauges, FSI's, GPS's, VOR's, NDB's, DME's, ILS, IFR, VFR, and all the other aspects of flying that I don't have time to type with "the speed limit is 65 mph".
IMHO, there's just no comparison here...