The quality of supermarket ground beef here in northern NJ has plummeted in recent years. Sure, for the most part, it's ground locally, but... from what?
Ground beef has a tendency to be the butchers garbage disposal. It usually has some cryovaced round, but it almost always contains old roasts that have been sitting in the case and that never sold. The only thing that varies from store to store is how long they leave the roasts in the case before they grind them.
Over the course of about a year, in a quest to get a half decent hamburger, I tried ground beef from every single supermarket in a 20 mile radius- on multiple occasions. 3 different Shop Rites, 2 Pathmarks, 2 Kings, A&P, Acme and Foodtown. Kings was the worst. Considering their upscale clientele, I found it surprising, but on a few occasions, I couldn't even eat the meat it was so bad. A&P was second to last. I've actually stopped buying A&P meat in it's entirety. Pathmark, Acme and Foodtown were all barely tolerable. And, just a skitch above that, was Parsippany SR. It's not like Parsippany SR was good, just not quite as foul as the other places.
It's a bit of a distance, but when I was down in Bridgewater Wegmans buying rennet for mozzarella, I decided to give their family pack ground beef a shot and was amazed by the quality. It was the best hamburger I've had in years. I've since returned to buy another two 6 lb packages and those seem to be winners as well. With ground beef, it's always a crap shoot depending on who's working that day, but, so far, Wegmans has done right by me. I don't know how far 'north' you are in 'north Jersey,' but if you can take a trip down 287/202, I don't think you'll be disappointed.
I'm sure Whole Paycheck would give you something pretty good, if you're near one of those, although I have, firsthand, witnessed the assistant butcher asking the butcher what to do with the roasts he was pulling from the case. Without a pause, the butcher replied "grind them." The roasts were pretty fresh, though, and from the times I've had ground beef from WF, it's been good. But pricey.
There are some supermarkets that will grind meat for you (SR, mostly), but then you have to wait until bottom round goes on sale, and you have to get there at the time of the day when they still have some beef fat on hand. I've also run into SR butchers who will grind the round, but not the fat ("The fat clogs up our machines"). Jerks

I haven't completely given up on this route, but, I have to admit, I'd much rather take a 25 minute drive to Wegmans than go through the hassle of having a butcher grind meat for me.
I really hope that the economy is at fault for the crummy ground beef (less roasts being sold? tighter butcher budgets? Corner cutting on cryovac meat processing?). This is just way too much trouble to get a half decent cheeseburger.