One of the greatest stories ever put to film, and maybe more times than any other story I can recall, would be Dickens' A Christmas Carol. I try to watch at least a few versions of this every year, but with 200 films, TV episodes, or animations of this story from major studios and maybe several hundred more less well-known, I suspect very few have seen them all. Hell, Sanford and Son even did an episode called Ebenezer Sanford (1975)
Which is best? I've always been partial to the Reginald Owen version from 1938. Most seem to cite the Alstair Sim version from 1951, but I honestly never understood that. But even the Reginald Owen version is not "best", it's just a personal favorite.
Ironically, the one that's probably the most well-done and true to the book is the one Jim Carrey and Gary Oldman did with Disney in 2009. If there had to be one "best", despite being animated, this is probably the one.
There was a very cool and rather dark version done in 1971, animated short at 26 minutes, made to fit a standard half-hour TV block. It was a fun one to watch with the kids when they were young, and attention spans too short to watch a feature-length movie. That one had Alastair Sim return to do the voice of Scrooge, and again it's not the "best", just another personal favorite.
Bill Murray's "Scrooged" is also always a fun watch, 1988. Love the Bobcat Goldthwait character, in that one.
