Love every season
Maybe it's because I binge watched all 5 seasons in one weekend, but I haven't noticed any significant decline in quality. I feel like it is still the same show, about dudes who do stupid stuff all the time, and is still hilarious. Dorm Daze is definitely one of my all time favourite episodes for the show. I feel the same way about Its always Sunny in Philadelphia, loved every season (yes some might rank a bit higher) but overall I feel it has been consistently funny from the start.
Maybe it is just my nature to overlook decline in quality, but there have been many examples of my favorite shows that I admit to having a huge drop in quality. But either way I feel this show is just as funny as it was when it first came out.