I'll second that, Yanq. I'm a Rockland County boy--first county in NY north of Jersey (just north of Bergen, actually)--and New Jersey is just what it is. Yes, the part of it that abuts NYC can be atrocious; I commuted from Upper Manhattan to Princeton from 1994 to 2000 and drove that stretch of the Jersey Turnpike (exit 18 to exit 9) more times than I wanted to. New Brunswick is nobody's idea of a good time--no runner's at least. Yet even there I'm sure I'm exaggerating; no doubt Rutgers XC has good routes figured out.
Princeton is great running; in the spring it's dizzyingly beautiful along the towpath, the old Erie Raritan canal. If you want mountains, you can find them in the northwestern part of the state, where Vernon Valley / Great Gorge is, or used to be. (I used to drive out there to ski.) I've canoed on Jersey rivers; there are parts of the state that are wild, rustic, almost like Deliverance. (On second thought, that may not recommend the state to doubters.)
I can't speak for the shore, since I don't know it. The "foot" of the state includes the Pine Barrens--which I suspect is great territory for ultra runners--and the "Garden" part of the state: farming country, blueberries and the like. Hammondton. You haven't really seen New Jersey if you haven't seen that part.
It's the Turnpike from New Brunswick on up that gets the state a bad name--the smell is distinctive--and the decaying urban infrastructure in some of those northern city-ettes. Even Newark, though, has its redeeming points. One of the greatest jazz radio stations in the country, WBGO-FM 88.3 (available by webcast), has anchored Newark since 1980. Bob Porter produces "Portraits in Blue" out of the station. I've volunteered there during several fund drives. Great people, great place.
Even the middle part of the state has lots of wooded old small towns. Rich folk, horse people, know all about them. Once I drove from Princeton back to Rockland County via Rt. 202, which meanders up through the state, missing all the "ugly Jersey" stuff.
So, no: anybody who simply writes the state off is doing so from ignorance. They're confusing an admittedly ugly part with the quite varied and often beautiful whole.
I haven't even mentioned all those rural counties to the West, towards Pennsylvania & Bucks County. Hunterdon County? Exurban, small-town America. Horse country. New Jersey has lots of horse country; part of the state rival Lexington, Kentucky and bluegrass country.