I do not see how it is possible to get grease where it needs to go (between the load bearing surfaces) on the stock ball joints using a grease gun.
Hellbound13 told you how - with the needle.
I've go 47,000 miles, including 5,000 with a lift and 35s with no issues on the ball joints. Every complex mechanical system can be characterized by a bell curve of experience with failures. Don't paint the whole population of vehicles as flawed becuase yours is the one that failed. Sucks for you but doesn't mean the lot of them suck.
2007 JK 2dr Rubicon, 3" Black Diamond Lift, 35" KM2s, M/T Classic IIs, Rancho shocks, Mopar bumpers, 8000 lb winch, Ace rock sliders, Skid Row engine/oil pan skid, evap skid, Tom Woods driveshafts, Riddler diff covers, rear adjustable upper control arms, chromoly rear shafts, Reid knuckles, Synergy chromoly tie rod, track bar, and flipped drag link.