Being a an equal member of the reading and watching public, and having more than the average understanding about what goes into bringing any previous work to film, I always approach filmed versions with a grain of salt.
I do not think I have ever been pleased with a depiction of any Agatha Christie novel. For some reason, the endings of these seem to be less than sacrosanct to writers and producers. Do not ask me why.
Also, it is usually very hard for every nuance a writer brings to her work to translate well onto the screen.
Yet, Suchet's charm has always seemed infectious to me. His Belgian eccentricities always make Poirot come alive to me. I may be overstating this for most tastes, yet, I can opine that Suchet has a way of transcending any plot mischiefs or storyline inaccuracies and makes every experience with Poirot a delight.
Such was the case with The Murder of Roger Ackroyd. It was finely wrought and delicately portrayed in a way that pleased what little I know of what life was like then. If there was much lacking from the book, all I can say is that I certainly expected it and I adapted to it unbegrudgingly. If I want true and complete Christie every time: I will read her books. They are the true source of this brand of pleasure aren't they?