Correct -- I looked up some info on Neptune; it can't be seen with the unaided eye. It is a magnitude of around 7.5; anything about 6 or so is considered not visible with no magnification. Saturn, by contrast, is a magnitude of around 1 (varies seasonally and with the orientation of the rings).
Interesting fact about Neptune that is pretty impressive, that I stumbled across when looking up its magnitude: "Neptune is not visible to the unaided eye and is the only planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier."