It's simple to be so sure because this show has everything.
A true concept: for a rare time, the production didn't submit to conformism but chose rebellion. Bye bye the courageous doctors, the honorable lawyers or detective, here, the main characters are a couch potatoes mother and a shoes salesman father. In other words, networks were discovering that there was an untapped world of inspiration, that's to say, the plain reality, that's to say the lives of common people!
An inspired creative team: you can pick any episodes, it's fun and you laugh very hard. It's an amazing feat because it lasts all the episodes during 11 seasons! Their stock of fun was also very particular: sex clichés, couple relationships, neighbors friendships, American way of life (tv, sports, cars), money, loosy jobs. Well, everything that everyone can face in its real life except for sure if you are the always happy family of the other elitist sitcoms, making a good lot of money and void of any consciousness of its own. In addition, that pool of gifted writers really knew how to put their crazy ideas into lines and build coherent script where everything is used to make fun. Thus, the 23 minutes are fast paced as all the jokes are delightfully crafted and oiled a delicate mechanism as the best comedy needs.
At last, an amazing cast: All were truly excellent artists with evident comedy skills. Each knew how to portray their characters with a few distinctive traits and could make in addition, funny faces, funny voices. Sure, i have not heard of any of them since but this Bundy and Rhoades families are always in my heart!
To conclude, contrary to the opinions that would rate this show as sexist, macho, crude, coarse, insulting or depraved, i think it's united around strong morals values (sure told in a crazy ways!) and acknowledges that humans aren't gods or robots but imperfect people.
When i review a show, i pick always my best episode of the season. Here, even with a shortened season, it's hard to choose. The wedding anniversary (1.6), the patrol dog (1.3), the poker party (1.8) were irresistible but finally i choose the last show because it's like a play with people coming in and out, and Al has terrific lines with everyone or everything (especially, the instruction manual!)