Is Cheers still worth watching? Does it hold up? Why isn't it as popular as Seinfeld, Friends or even Frasier?

"Cheers" might not be as popular today but go back some 20 years and it was on TV just as much as the other shows you mentioned.

People talk about Cheers all the time.  It is favorite series.  People don't talk about the wonder years a lot.  But they do.  People don't talk about Buffy the vampire slayer all the time but they do.  Cheers developed a cult following and people talk about it.  Just like they talk about Frasier.  Take like NYPD Blue or Hillstreet Blues it was very popular and won a lot of emmys.  Not a lot of people talk about it very much.  It developed a cult following.  Just like The BIg Bang Theory it developed a cult following, a lot of people talk about it. 

I think a good question is, does a show like CHEERS deserve a reboot?

I don't think Cheers does, I tried rewatching it and it was boring, Seinfeld even more so, cannot watch it.

Friends holds up, it seems always watchable...other sitcoms that stayed funny: Less than Perfect, Just Shoot Me (at least the first two seasons), and maybe Dharma and Greg.

I grew up watching

"Cheers" Never cared for  "Seinfield" "Friends" and "Frasier"

Better than most "comedy" shows on TV today.

As someone who for a while didn't like tv, then got into modern shows and have gone back to check out some classics, I've had fun with what I've watched of Cheers. Some of the humor/way of speaking is pretty dated, but I think the acting/characters shine through at times and make it worth checking out. There's an early episode, either season 1 or 2, where the main guy Sam Malone, he owns a bar but he's a former alcoholic now sober, and he has a string of bad luck and is sitting there towards the end just staring at a shot and thinking about drinking it, and I thought that episode was really well done. Also I think Diane the main girl is pretty cute and funny so when an episode is about her I enjoy it. But yeah I'd say check it out for yourself and you might enjoy it. 

It's entertainment not world councling.

It was popular in its own way.

I find that all older comedies lose their amusement.  The shock or surprise, which is a main source of humor, is no longer either surprising or shocking, so while it might be amusing, it is not hilarious.  This applies to Seinfeld, Cheers, MASH, and even I Love Lucy, if you want a range of comedies from the past.

I mean, Master of Your Domain and Shrinkage, from Seinfeld, knocked me on my tail the first time I saw them.  Bassomatic or Landshark at the door from SNL were over the top at the time.  But now they aren't much different from watching an old WC Fields movie.  Dated. Still amusing, but not FUNNY.