yes you can watch movies in your stateroom, they are not new releases,but not too old either - for example we cruised this Feb and we caught "School of Rock" and "Maid in Manhatten". Depending upon which ship you are sailing on you might have "Movies Under the Stars"- outdoor movie theatre by the pool, showing more current movies.
On the Diamond, they have a theater, pretty good movies showing, Something's gotta give, Calendar girls, and so on. We didn't watch much t.v. in the room, but there were a few good movies playing in the evening.
On one of our cruises, I think it was the Golden, in 2001 (whatever year Chocolat and A Knight's Tale came out) we saw the movies in the Princess Theater, and then discovered that the same one was on the TV the following morning in the cabin. If the movies are obtained through satellite, then the showings might be geared to the schedule of the signal, or channel--HBO? I don't think it deters from anything and there's nothing wrong with it-I was just surprised, and if I wanted, could watch the movie again and pick up what I missed on the big screen. I don't know if that is still the case or procedure.
I was on the Diamond with Shellu U. and I preferred watching the movie on the in-room TV. The projection system on the Diamond isn't that good. Instead of an actual projection, you're seeing a giant monitor because the movie is on a DVD. The resolution isn't that good and it's kind of dim. Nowhere near what you get in a regular theatre.
The movies are FIRST run. They play them in various lounges...sometimes good sometimes bad as far as the seating and quality of picture. They also broadcast movies on the TV. This was great as my travel partner is handicapped. He was thrilled to have something to do in the room. One day he watched a different movie from 7:00 am till 10 Pm that night.