We hardcore Harry Potter fans get into the dumbest raging debates. Most of them center around the movies, although a personal favorite of mine has to be the whole Harry/Hermione "ship." I recall on one forum seeing the words "To me that's the cannon ship!" typed out by one fangirl with such gusto I could practically hear the shrillness of her voice as if she'd actually said it standing right in front of me. And the word "canon" was always misspelled and abused by these people. So my friends and I started a very amusing little fanfic of our own once about pirates on a cannon ship coming to blow up a bunch of annoying fangirls. Or something like that. It was all very snarky and nerdy and fangirly in its own way.
But the biggie that's ongoing is the whole "Who's the better Dumbledore, Richard Harris or Michael Gambon?" A great number of people prefer Richard Harris and actively despise Michael Gambon (who took over the whole after Harris died); I submit that the Harris preferers don't really know Dumbledore. The Dumbledore described in the books is ancient but quite spry up till the 6th book, at which time he's suffered a terminal curse wound; even then, he still manages to maintain his sense of humor -- a sense of humor that was always a bit on the melodramatic and campy side. There's a moment in Prisoner of Azkaban when Dumbledore is described as having "bounded up the staircase." This is how Michael Gambon's Dumbledore behaves in the movie, and I have to say, watching how close to the end of life Richard Harris clearly was while filming the Chamber of Secrets movie, there's no way in hell he was going to be "bounding" anyplace during a third outing as the character. There are times when it feels like he can barely speak the lines in his scenes. I can't fathom him having made it through four more movies after that.
Harris gave us a regal, intimidating and vaguely mysterious Dumbledore. Gambon gives us the twinkle-eyed aging wizard of the books with the sense of humor only eclipsed by that of the Weasley twins. There are a couple of moments when he's downright ditzy or even doddering, just like he's described by his detractors in the books -- the bit in Azkaban when he pats Ron's broken leg absentmindedly while waxing rhapsodic about the wisdom of listening to children springs immediately to mind; this is a moment that the haters hate and the Gambon lovers love. And this is where the debate comes in, because the two actors play Dumbledore two very different ways. There is a camp of people whose view of Dumbledore is the view of Dumbledore Harry has in the first two books, and whose view of Dumbledore didn't change and grow with Harry's as they made their way through subsequent volumes. These are the people who claim Dumbledore is acting out of character in the 5th book, Order of the Phoenix, when he avoids contact with Harry throughout the school year, believing he is acting in Harry's best interest; but these same fans reserve the right to be angry with Harry over his (well-placed) anger at Dumbledore throughout that book.
To me, Harry learns in his journey from year one to year seven that Dumbledore is just as Percy Weasley describes him on Harry's very first night at Hogwarts: "Brilliant. The best. But a bit mad, yes." In the end, Harry accepts Dumbledore just as he is, warts and all, but it takes him a long time to get there, because in the beginning, he sees Dumbledore as a hero, infallible and worship-worthy. He doesn't see him as just a man like everyone else, with foibles and quirks and the ability to make mistakes. Gambon portrays Dumbledore as Harry's Dumbledore at any given moment. By the 6th movie, early on, we hear Harry say to Mrs. Weasley with a shrug when she asks what he's doing at the Burrow unexpectedly, "Dumbledore." Leaving unspoken what we're meant to empathize with -- "Who knows why Dumbledore does anything the way he does it? We're all just along for the ride." And this sets the narrative of the movies up neatly for what's to come in the final films -- Harry's quest to find the Horcruxes combined with his quest to understand, really and truly, Dumbledore.
My biggest problem is that I can't envision Richard Harris playing a vulnerable Dumbledore. I can't imagine him with the catch in his voice in the 6th movie when Gambon as Dumbledore says his final words: "Severus, please." And Harris was so elderly and tired-seeming in the first two films that I've never been able to imagine him visibly aging in front of Harry's eyes from movie one to movie four, when Harry first realizes just how old Dumbledore actually is. And by the same token, I can't picture Harris capable of the crackling, palpable anger Gambon carries off in his battle with Voldemort at the end of the fifth movie.
I think the thing that annoys me the most about the debate though is the whole ability of pro-Harris people to forget that Richard Harris is dead. That left precious few actors capable of fulfilling the role. Legend has it that Gandalf himself (Ian McKellan) turned the role down; since he is the only other actor the pro-Harris brigade ever cites as being able to portray the Dumbledore they envision, I think there comes a point where you just need to get over it and accept and appreciate what you've got. And what we've got is a better, more true Dumbledore. Harry's Dumbledore. JK Rowling's Dumbledore.