OP mentioned on-road routes. Here are a few I like:
Far North Jersey (north of Newark):
9-W North is a lot of fun. Take Palisades Parkway north from Englewood Cliffs to just before the NY/NJ state line and exit at 9W. Takes you along the Hudson River:
Central/North NJ: Schley Mountain
Lightly policed, be careful on the segment north of Mine Brook Road around the lake. Otherwise many awesome curves with great lines of sight.
Central NJ: Delaware River
Great ride up the Delaware. Probably even more fun in the summer.