My favorite Counties are:
Hunterdon
Pros: Really nice scenery and enormous land parcels.
Cons: You have to drive ALOT to reach anything.
Passaic
Pros: I grew up in this county!

It's very down-to-earth, especially compared to its neighbors. The taxes are lower too.
Cons: Passaic and Paterson need TLC. Some good changes are already occuring however.
My least favorite County:
Hudson
Pro: close to NYC
Cons: the population density there is not my cup of tea. "Stereotypical" NJ is in or around this area. The only decent towns there are Hoboken, Secaucus, and Kearny. And these are just ok.
Overall I like Central Jersey best (Hunterdon, Somerset, Monmonth, and Middlesex). I like this area alot because of the diverse neighborhoods and how the "wealth" seems to be more distributed in that part of the state. Most people seem to be middle to upper-middle class in that part of Jersey; be they White, African-American, Asian, or Hispanic.