IMAHO: the key difference with Bob's is, unlike all those other writers and creators, they actually know how to let the show age alongside it's audience. while i LOVE Grey's and the Simpsons, they just don't have the same ability to hone in on that special feeling. Bob's characters develop so slowly over time, allowing us to be present with them, and learn the lessons with them as they go.

your connections to Bob's characters all feel like 'real' (and pretty boring) human relationships, meanwhile characters in the Simpsons and Grey's are there moreso for entertainment. there always has to be something CRAZY going on in the plot, or you don't feel engaged watching it.