For A Christmas Carol, it's Alistair Sim for me all the way, baby. I have actually not even seen most other film and TV adaptations. I only remember, as a kid, being less interested in the Reginald Owen film version.
However, the other night TCM was running a bunch of them and I caught just a few minutes of the 1964 TV movie A Carol for Another Christmas which I'd never seen, and it looked wonderful. Written by Rod Serling, directed by Joseph L. Mankiewicz, starring the likes of Sterling Hayden, Eva Marie Saint, Ben Gazzara and others, with a score by Henry Mancini -- what's not to like? I am truly sorry I didn't get to watch or DVR it.
(I don't suppose DR George or anyone DVR'ed it? hmm? hmm?)