Although mario, pong, pacman, etc. were the "first" of their kind they are not neccessarily considered "the best" of "all time." Just as the first mac computer is probably not considered the "best" of all time just the first. It changed the whole landscape of electronics, but still doesn't make it the "best of all time."
I guess when you said the father of modern sitcoms I took that too literal. As in comedy sketches at the begining of shows and new york apartments. However, what really comes across to me is sitcoms building off other sitcoms just as Macintosh computers have been built off of. For example, you mentioned it being the first to show that sitcoms don't have to revolve around a single household, but what about dukes of hazard. Not only did it not revolve around a single household, but the characters were zaney and you could say they were the first to do horrible things and yet people loved them. It also did not revolve around a single household. So it's not like modetn sitcoms stole or took ideas specifically from "that" show, but rather sitcoms build off each other. The 3 stooges hurt each other for self enjoyment. Etc.
Don't confuse the first with the best. Also, understand that all sitcoms have built off each other. You make good points that it is innovative for it's time, but just as people aren't walking around with brick cell phones or an 80's computer, because they are not the best availible so to Sienfield may not be the best ever.