I could watch only Gintama for the rest of my life and be satisfied as an anime viewer. This is 400+ episodes of consistent satire that works as a parody of otaku culture (anime, manga, video games, merchandise, obsession with idols), Western pop culture (several american celebs make appearances), and is a commentary on Japanese lifestyles and lost traditions that are represented through the dozens of personalities in the show. The characters may seem like one dimensional punchlines at first glance, but there is always an arc that explores them in a way that is relatable and endearing to the viewer. Eventually after watching the same personalities living in the same environment interact with each other over and over again, it can feel like a living community that you're excited to see the progress of with every new episode. Very similar to the experience of watching a great sitcom for a long time. At that point you're forever hooked on Gintama and it can never end.
This is probably the most referenced anime on youtube. There are thousands of clips that can summarize the appeal of the comedy. One of my favorites is Gintoki getting caught practicing a Kamehameha. Anybody who grew up watching DBZ or superpower cartoons in general has tried to mimic special moves in a mirror with nobody around, and that person can feel second hand shame for Gintoki getting caught doing something that looks very stupid in reality. Gintama really understands the viewer and tries to appeal to them with jokes like that
Another is when Gintoki makes that dramatic entrance that all shonen heroes do to save the day. He deflects a bunch of kunai to save a child from being killed. very cool. Except he missed a couple. and now he's bleeding. and so is the child. But he has to pretend as if he's totally fine because he's the main character.
Another is when they break the fourth wall to criticize the animation staff for not completing an episode. leads to a MS paint version of a Gintama OP which is the funniest thing I've ever seen a staff do to their own show
and we get a background look into the animation process, both educational and funny
The comedy makes it pretty jarring when Gintama shifts to a battle arc every so often. Though it makes fun of shounen tropes a lot, it still is a shounen and embraces that when there's a boss that the community has to come together to defeat. There are certain scenes in this show that can rival just about anything in the genre in terms of hype and emotion. to the point that you think established characters are about to be killed off.
The intimidating episode count and the sheer amount of references to other anime is the usual reason people don't like it. It can feel sometimes like you need to do some research in order to understand what they're even making fun of. and you do need to watch a couple episodes before it grows on you, not an immediate hook like other shows can be. For this reason it took me forever to start Gintama, but once I did it eventually became a personal favorite and now I think it's a top eight anime ever. Easy 10.