It's the only one I've never finished. I keep wanting to play it but I never do. Bought it on day one for Xbox 360 and somewhere along the way, my enjoyment just died out. I've gone back and totally replayed every other game in the series multiple times. After Gears 4 got the 4K update, I began to replay all of the games again from the first one. I made it to about 2/3 of Gears 3 before getting distracted by some other game--but the whole time, I was thinking "I'll finally finish Judgment...but do I want to finish Judgment?"
I was underwhelmed by Gears of War 4, too. Hyped for Gears 5.