The movie doesn’t really fit on a two-position sucks/rocks scale; technically it was brilliant, but as a human story it was weak. As others have stated, there were lots of true stories aboard ship that would have been more interesting than the hackneyed poor boy - rich girl tripe.
The movie did a great job of showing what a huge, magnificent vessel the ship was, and also how isolated (a high overhead shot of the liner at night, its bright portholes the only light in a huge, dark ocean, literally gave me chills). And the sinking was amazing.
But somehow Cameron didn’t think the huge tragedy was dramatic enough. It’s not enough that our annoying young lovers are aboard the most famous sinking ship in history – no, they have to suffer a false accusation, endless wading through frigid water belowdecks, and then being chased and shot at by the completely superfluous “villain”. Typical excess.
My favorite scenes didn’t involve randy little Rose and Leo, but were about either real people or believable situations – the mother silently holding her two children on the bunk as the water rises in their cabin; the ship’s designer making a small adjustment to the clock in the main salon as the ship is noticeably tilting towards the bow. It didn’t even bother me that Cameron used the cinematic chestnut of the band playing “Nearer My God to Thee”, which they probably didn’t – the beautiful, sad melody worked perfectly for that scene.
(Incidentally, they did not lock the steerage passengers in, nor was the Captain trying to set a speed record.)
Cameron has a great visual sense, but little imagination when it comes to characters. (Who thought it was a good idea to have an upper-class, educated young woman in 1912 give her despicable fiance the finger, for Christ’s sake, instead of saying something pithy that would have put him in his place?)
The sets and costumes were near-perfect. (Sadly, some of the costumes were actual vintage pieces and were ruined by water for the sake of making a movie; a lot of costumers are not happy about that aspect.)
So I’d give the movie two and a half stars. If it had had a really good script, and a more subtle director (maybe with Cameron in charge of the second unit), it could have been great.