The thing that I think makes the Fresh Prince great is that so many people watched it, from all different backgrounds, ethnicities, genders, and colors. It doesn't matter if they like slapstick, low-brow humor, or more intelligent, sophisticated humor.
There have been multiple occassions when I've been hanging out with a bunch of people from all different walks of life, with completely different interests, and somebody is flipping through the channels but no one can agree on what to watch. Then Fresh Prince comes on and everyone is happy.
I don't know about the over 30 crowd, but I think this definitely true for the under 30 crowd.
I know people who don't like shows like Seinfeld, Friends, Frasier, 24, X-Files, whatever. I don't know anybody who doesn't like Fresh Prince.
If you have different types of friends, test it out. Ask a friend from an upper class walk of life if they like Fresh Prince, then ask a lower class friend. Ask a white person, ask a black person, ask a hispanic person. Ask a person who doesn't really watch sitcoms, ask a person who only watches dramas or reality programs. Ask a person who likes hip hop, ask a person who likes rock. Ask someone with a dry sense of humor, ask someone with a slap stick sense of humor. I'm telling you almost everyone likes Fresh Prince. Now if you asked this same wide range of people about any other show on the list, I don't think any show will be as universally liked as Fresh Prince. This doesn't necessarily make Fresh Prince the best, but I think it definitely says something about the show.