It's a failing of the flight dynamics of the simulator program. It's difficult to compare a computer controlled sidestick aeroplane with a manual control wheel aeroplane as not that many people have flown both. The 737 is not renowned for being 'sluggish'. I have flown the 737-200 and -400, and both are quite perky, the -200 in its BA guise being skittishly so.
I've tried out FS2004 and with failings in the joystick department giving very 'flat' feel, there is little realism. The novelty is seeing how convincing these sims are in operation, but do not feel there is any realism.