No, no, no. Calm down. I know what you're about to say. Just hear me out.
For the movie-maker, Moby-Dick is, like any other brick-sized tome, very problematic. There is just too much stuff, and unless one has the luxury of filming a five-hour movie and releasing it in installments (see Harry Potter and the Deathly Hallows), material has to be cut, and the story amended accordingly so it will make sense with the cuts. This sort of boiling-down is fine for relatively simple books (such as, again, Harry Potter), but not with the likes of Moby-Dick. Not only is there a lot of stuff, but almost all of it is important! This is where the other movies fail. They try to be too literal and everything just ends up getting swamped by spectacle.
Consider the first three. The first, with John Barrymore (1930), misses the point with such a breathtaking completeness that it is only worth mentioning because it exists. The second, with Gregory Peck (1956), is ambitious, and does a few things well, but Ray Bradbury's lackluster screenplay, and his strained relationship to the director, bulldoze any chance of overall success. The third, with Patrick Stewart (1998), is a bizarre, half-assed, condescending, wishy-washy mess which isn't just a little boring.
So what did they do here? How did they juggle all the stuff in Moby-Dick? Simple. They didn't.
Instead, they stuck to the barest bones of the story, only those things absolutely essential--Elijah, the encounter with the Rachel, Ahab's first speech to the crew, and so on--and threw out everything else to focus on the characters. By doing this, Melville's fundamental themes, the very reasons Moby-Dick is as compelling as it is in the first place, are thrown into relief. Ahab becomes Jonah. The whale himself becomes the unattainable goal, the inability to escape fate. The questions of friendship, loyalty, equality among men, hubris, prophesy, the existance of God: it's all there.
One might be a little jarred, at first, when the movie begins and then almost immediately diverges, and drastically, at that, from Melville, but all one needs is to wait a few minutes to see William Hurt as Ahab to be hooked. He is excellent, charismatic, haunting, and blows Gregory Peck's frustratingly one-dimensional Ahab clear out of the water (hint: Peck himself wasn't satisfied with the movie). The acting is good in general, but William Hurt takes over the camera. This Moby-Dick is worth watching if only to see him as Ahab.
My overall impression: Impressive, sweeping, riveting, epic, and in all other ways superb. A few small pacing problems bog things down a bit after the halfway point, but they're manageable. My one regret is that the final showdown with the whale wasn't as colossal as it is in the book: Ahab grappling with his lower jaw, for instance. It would also be nice if there were a proper title sequence, but that's just an annoying trend in movies in general.
Otherwise, beautiful. If nothing, check it out just to see William Hurt and the gorgeous camerawork.