The first TV Show: #421 The Simpsons
The first show to be watched is one that I'm mostly going in for because I've been watching it a lot for a while (as well as getting a lot of the lore through The Simpsons: Tapped Out mobile game). As a long running show (not the longest running cartoon - thanks Japan, a shame we won't get to see your animated work) it really has gone through its own ups and downs. Aside from having started on the most recent seasons (keeping up to date) my current watching has gotten me into season 7.
This is still the high point of the series - where that ends is debatable, but I know it's coming up - but I'd argue that even the lower points (of which I've sampled a few while writing up) are still good, just not as good. One of the genius parts of the early shows are how they link together several different plotlines into one in a way that makes sense, while keeping them all enjoyable. This allows them to mix the ridiculous with the grounded in an episode - keeping them separate until needed.
At the same time, the show has good concept episodes, whether it's one of the several story episodes (which allows for smaller stories to develop, set in weirder environments) like the celebrated Treehouse of Horrors series, or a look at the family's future.
One of the biggest advantages The Simpsons has, in part because as an animated series it's easy to introduce more, is its extended cast. There's are loads of additional recognisable characters that get used when needed, allowing the titular family to be sidelines as story requires (without having to worry about the actors not appearing). Just as often, minor one gag characters return and become more fully fleshed-out characters.
It's been good. You could wonder whether it's time the show ends, but until then there are a lot of good episodes to watch even now.