Daniel Radcliffe cannot act. Seriously. There is scarcely a scene in the whole film in which Harry shows any real depth of emotion, be it wonder or fear or anxiety or anger; in fact, no matter what spectacular marvels or stunning horrors take place in front of Harry's eyes -- from the very beginning of the movie when he first learns of his wizardly heritage to the end when he confronts Voldemort -- Radcliffe's expression hardly changes. Even when he tries to put emotion into his voice, it never reaches his eyes, never animates his face.
Oh, sure, Radcliffe looks the part -- I've no quarrel with that. I don't even care that his hair isn't quite messy enough or that his eyes aren't green. He's a cute kid, and I want to believe that he can play Harry. But in this movie at least, he doesn't do much of anything. Especially compared to Rupert Grint as Ron, who really does know how to portray emotion effectively and convincingly (just watch him in the chess scene) and has very few scenes that fall flat. Even Emma Watson as Hermione, though her performance is somewhat uneven in quality and at times overplayed, at least shows some real animation: but Daniel Radcliffe just appears to sleepwalk through the movie. In fact, without in the least feeling like I'm being unjust or overstating my case, I would say that he is by far the worst actor in the whole film.
Still, like I said before, I want to enjoy watching Daniel as Harry, and I wouldn't want somebody like Haley Joel Osment to take his place, so I'll certainly be keeping my eyes open for him in the next film, and hoping his ability to play the part improves. I just have to say that I'm baffled by all the accolades that Radcliffe received for playing Harry in the first movie, because frankly, I don't see that his performance was anything to write home about.