There have been many TV series with charm; some have certainly stood out over the years. But after awhile most of them seem to be the same thing. I haven't watched regular TV for years. Once in a while, I hear about a standout series that has been around a while, or has even stopped production by the time I learned of it; it was that way with "Will and Grace," which I ended up liking very much in syndication.
But if I had to choose an all-time favorite, I think it would be a sitcom from the 1960s, the original "Dick Van Dyke Show," with Mary Tyler Moore, Rose Marie and Morey Amsterdam. Maybe you had to grow up in that era. It was one of those shows that quit production when they were still at the top of their game; they didn't want to become stale, drop in quality and die an ugly reputational death.
While I'm basically a movie person, I have bought several TV series over the years, including "Will and Grace" and "Are You Being Served?" But the "Dick Van Dyke Show" was the first, and my favorite.