I Love Lucy will literally always hold up, despite the show turning 72 years old this year. I'm not going to say I'm a dedicated Lucy superfan or whatever, but hey if I'm just trying to find something to watch and see that it's on? I'll probably watch it.
What I am a superfan of, however, is Doctor Who. Which is still airing to this day, of course, but premiered all the way back in 1963. Favorite era of Doctor Who is Patrick Troughton's run as the Second Doctor from 1966 to 1969. Unfortunately, it's kind of hard to appreciate his era nowadays because of the 21 stories that were part of his era, only seven of them survive complete in the BBC's archives (and five of those stories are from season 6, his last season; two are from season 5, and no complete stories exist from season 4), although if you count for stories that had their missing episodes remade with animation, his era has 17 stories that you can watch.
Twilight Zone is really good too. I don't mind the later remakes (shout out to the episode from the 80s version where a character has died and finds out they're going to Hell but can't figure out why and thinks that it surely couldn't be just because he's gay, pretty powerful message for an episode from the mid-80s) but the original version with Rod Serling will always be the best.
I actually grew up watching a lot of reruns of older shows from the 50s to the 80s because I watched a lot of TV Land as a kid and this was back when Cartoon Network still regularly aired stuff like Scooby-Doo, Where Are You!, The Flintstones, The Jetsons, and other Hanna-Barbara cartoons. (Also Boomerang was my jam, I didn't get it on the basic cable I had at home, but I'd watch it a ton when I was at my mom's during the summer). I'd definitely say that while I enjoyed stuff like The Andy Griffith Show, Leave it to Beaver, All in the Family (probably shouldn't have been watching that as a kid tbh), Sanford and Son, The Jeffersons, etc., the cartoons I watched growing up were definitely my faves.
Of course, can't forget things like Looney Tunes, Merry Melodies, Popeye, The Three Stooges and various other theatrical cartoons and shorts that later got second wind in television syndication. I try to watch MeTV's weekday and Saturday morning cartoons as often as I can. Crazy how in 2023, we got Looney Tunes airing in broadcast syndication again and not just on cable or streaming.