--Not favorite characters, but ones who were done the best in the movies.
--Characters who have a big impact.
Side note--I tried filling 25 spots and couldn't really, so mine is a top 20 list. Counting up from the bottom:
20--Dobby and Kreacher
I like the way the house elves were done, although Dobby's character gets short-changed in the movies. Kreacher possibly isn't quite creepy or hostile enough, but that's okay. And I wish they hadn't skipped all of Dobby's fantastic fashion choices after he is freed, because those are half the fun.
"Students out of bed! Students in the corridors!"
You just have to love Filch. And by "love," I obviously mean "be creeped out by, and sort of hate, but maybe also feel a tiny bit sorry for."
Narcissa doesn't get much face time in the movies or the books, but I love her character. Death Eater she might be, but she is also a mother who will risk anything for her [slimy rotten but in the end possibly halfway decent] son, and I respect that. In at least one way, she's not so different from Lily Potter or Molly Weasley--in fact, you could almost think it might be a case of just having gotten in with the wrong crowd, one that's not too easy to leave when you change your mind.
"Good lord, boy, they told me you were intelligent."
I wish she'd had a bigger role, because I think the movie Mrs. Figg is just so lovable. I even like her better than the book Mrs. Figg, just love how they did her.
"You need to know what you're up against! You need to be prepared! You need to find another place to put your chewing gum besides the underside of your desk, Mr. Finnigan!"
My only complaint about Moody is that I don't remember him saying "Constant vigilance" in the movies, and I don't know why they left that out.
I think Lucius and Draco were done pretty much perfectly, even if Jason Isaacs's hair is a little bit Legolas-esque. Both did a good job going from unbelievably snooty evil creep to damaged and broken, and at times they even look enough alike to really be father and son.
I think everyone agrees that, from the beginning to the end, Matt Lewis was a good choice for Neville. (Also, it may interest you to learn that there appears to be an extensive world of Neville fanfiction out there. Who knew?)
I love Luna so much, in both the books and the movies. I wouldn't have suspected it from just seeing Evanna Lynch as she normally looks, but she is a fantastic Luna, and this is one of my favorite scenes in all of the last movie:
11--George and Fred Weasley
Ah, Fred and George. Where to begin? I don't think anyone's favorite character list doesn't include the Weasley twins. As far as their movie versions go, it's always made me very happy that they are played by actual twins, and not just one guy doubled up. (I think it allows me to secretly believe that the Weasley twins are real, and James and Oliver are just pseudonyms.) Unfortunately all their best quotes are in the books, not the movies--they, too, are seriously short-changed, which is understandable but still depressing.
Gary Oldman is an excellent Sirius Black, although I actually think he looks a little better as a disheveled Azkaban escapee than he does later on, all suited up and groomed. I think it's mostly the hair; it just looks weird all pretty and combed. My primary complaint about this character is that in the fourth movie, Harry writes him a letter and addresses it to Sirius Black. Later Sirius writes back and says to use a different owl because the Ministry might notice. Really?
"Mad and hairy? You wouldn't be talkin' about me, now, would you?"
I don't think they could have found a better person to play Hagrid than Robbie Coltrane, and they did a fairly good job of keeping all his quirks and side-stories in, too. Very well done.
8--Lord Voldemort/Tom Riddle
Ralph Fiennes as Lord Voldemort is one of the crowning achievements of the Harry Potter movies. The only reason I have him down so far on the list is that after a while, seeing him played by an actual human started taking the edge off his scariness. Nothing can compare to the imagination, I guess, but even besides that, I think somehow he just became too... regular. If you watch the graveyard scene in Goblet of Fire and compare that to the later movies, you can see a difference.
All the actors who played him at various younger ages were excellent, too; you could really almost think they were the same guy getting older, with the exception of the Chamber of Secrets Tom Riddle, who's a little more of a stretch.
It was so unfortunate that they had to cut most of Rita Skeeter out of the movie, because this character is just genius. The way Hermione figures out what's going on is brilliant, too, so it's a shame that part didn't make it in. But the dress, the glasses, the hair, Miranda Richardson--it's all just fantastic.
This guy is amazing. Chamber of Secrets is not the most exciting of the movies, but the fact that Gilderoy Lockhart is in it--played by Kenneth Branagh, who is five kinds of awesome--makes it so much fun to watch.
I really like what the Empire list said about Professor McGonagall: "Second only to Dumbledore in providing a sense of security and refuge at Hogwarts." This is why we love her--she's fair and she's strict and she's tough, and she is good at what she does.
I don't need to tell you how well Umbridge is done; the boiling rage you feel whenever you watch Order of the Phoenix is quite enough, I'm sure. The way I see it, any villain who can make me that angry is doing a really good job of being a villain. And I think it might be possible that there has never been a villain I've hated more.
Interesting tidbit I learned from the Empire list: Helen McCrory, the woman who played Narcissa, was actually originally cast as Bellatrix. When she got pregnant, they decided she would be Narcissa, and cast Helena Bonham-Carter instead. All I can say is, I can't imagine why HBC wasn't the very first person they went to, because she is perfect. I love her.
2--Albus Dumbledore (Richard Harris only)
I have a real issue with Movie Dumbledore. I think that Richard Harris was basically perfect, and I was really sad when he died. I also really like Michael Gambon--but I do not like him as Dumbledore. Not. At. All. He is basically a crabby old man who isn't even particularly nice to people, much less the incredibly kind, wise, sweetly eccentric man he's supposed to be. Maybe this was some kind of thing where they were trying to soften the blow of switching actors by having him not even try to fill Richard Harris's shoes, I don't know. But I don't like it, and in six movies it hasn't grown on me.
Professor Snape is probably the most complicated character in all of the HP world. Alan Rickman is one of my favorite actors in the regular world. I think this is a good combination. There are times throughout the series when I think he's just a tad cheesy, but I think everyone has those times. And not to spoil anything for people who haven't seen HP 7.2 yet, but he does some incredible acting in the final movie that only solidifies his place at the top of my list.
So that's it. You may be wondering why I left Ron, Harry, and Hermione off the list. The partial answer is that I kind of see them as a given; but also, they're too hard to fit into a list like this. They feel like they should automatically take spaces one through three, but do I really think that their acting was better than Snape and Bellatrix? So I've left them off, with the understanding that I think they were cast so well that I just think of them as actually being their characters.
And in closing, two thoughts on Empire's list:
1. I'm pretty sure the only reason Molly Weasley made it is the "not my daughter" moment. She's a lovely character (moreso in the books), but nothing that special until you throw in a girl fight and a mother figure pushed so far to her limit that she swears in front of her children, and then voila! Everyone loves it.
2. I agree with what they said about Tonks. Great character in the books; lame in the movies, and I don't see why she'd be on the list.
So. The end! What do you think? (I spent a really long time on this, so you'd all better share! I shake my fist at you if you don't.)