Albert Finny is my all time favorite Scrooge. It's hard to believe he was only 35 at the time as he played a 60 year old man so convincingly. He was also so gleefully nasty that he was such a delight to behold. What's more after Scrooge's turnaround the character was believably changed from within. That's hard to portray. Most Scrooge actors just seem like they're putting on a show of being redeemed so they don't end up going to hell. But Finny seemed changed at the end. Happier. Before when he walked he looked like he was dragging a ton of chains behind him. After he looked light as a feather like he was floating on air. I truly believed Scrooge's redemption in Finny's Scrooge and that for me is what makes him the best Scrooge of them all.
Second best for me would be Jim Carrey. Though that might be because I only first watched the movie within the last few weeks and am still excited by it. Wonderful adaptation. I liked a lot of the other versions but the Zemeckis version was just so visual and energetic that it felt like an all new story even though it was the same old one we've seen a million times.
Third best for me would be Patrick Stewart. Not in his version of A Christmas Carol but rather as Picard in All Good Things. I love how most people don't even notice AGT is clearly ACC but it's all there. Past, present and future. Character realizing he's not properly appreciated the people in his life. More social and kinder, embracing all those around him at the end. Wonderful adaptation.