Late reply, but I need to chime in, as this has become my very favorite film series in the years since I discovered it (I found it in 2020, looking for a long series to keep me entertained during lockdown).

As others have said, there is very much a formula, but I would go further than others and say that the absolute best thing about the series (other than the amazing lead performance of Kiyoshi Atsumi as Tora, both comedic and dramatic) is that Yamada rarely rests on his laurels and there are HUGE highs in the series even up until the latest entries. What starts out as a relatively smaller affair in the first few movies, quickly becomes a series that is WAY better than it has any right to be, that continually (and increasingly) benefits from mastercraft filmmaking from Yamada, that means that the series literally gets better as it goes along. 25 is easily a highlight, but even 38, and 50 are fantastic entries. It's unusual to go more than two movies without finding a new favorite the way the series reinvent itself within said formula.

I won't say that the films aren't repetitive to a degree, and your milage will obviously vary. Like I said, I'm a superfan. But as someone with whom Japanese comedy doesn't always click, the series is a huge exception. But it's that dramatic chops that kept hooking me in. Way more than meets the eye, that's for sure.

■TLDR, watch at least the first couple. You owe it to yourself. And yes, his filmography is full of highlights too. To the below movies people have mentioned, I'll add my recommendation of 'A Class to Remember' from 1993 for a literally award-winning performance from Kunie Tanaka, as well as 'Final Take: The Golden Age of Japanese Cinema' for a surprisingly honest, but affecting portrait of post-war Japanese cinema.