Only in my adult life did I read the stories, finding large chunks of the dialog in the TV show being word for word taken from the stories. And when not word for word, the tone and feel of the scenes so well portrayed on screen.
Yeah, I grew up watching that on PBS Mystery! and love it. I rewatched some of it as an adult and it holds up very well.
I also really liked David Suchet's Poirot. I still have yet to watch the last few seasons though.
However, I've never been much enamoured with the Miss Marple adaptations. Joan Hickson's is maybe the best (even though I prefer Geraldine McEwan as an actress) but I never took to it like Poirot.
You might like the nineties Jeeves and Wooster which stars Stephen Fry as Jeeves and Hugh Laurie (of House fame) as Bertie Wooster. It is formulaic but fun. I think it's the best thing Stephen Fry ever did.
There is a Soviet version of Sherlock Holmes which is surprisingly good starring Vasily Livanov. The locations sometimes don't quite look like England etc, but I really enjoyed it.
There are subtitled versions available online. Here is a short clip (with Sarabande over it)
https://m.youtube.com/watch?v=3Flnlb5ITNQ
I am a great fan of Brett's version, which I think is the best ever made. But I think the Soviet version is fantastic, considering it was made behind the Iron Curtain. There have, of course, been some awful Sherlock Holmes films but that's another matter.