I've since changed my view on this, but after watching LOTR: The Fellowship of the Ring in the cinema, I thought the ending was TERRIBLE! After 2+ hours in the cinema and it simply ends with Frodo and Sam standing there looking at Mordor was a real "WTF" moment for me. But in context, I now think it works and I consider the first of the trilogy to be the best.
To be fair, that's exactly where the book ended. In fact, the film has more of a climax than the book does, which doesn't have Boromir's death occur until the very beginning of The Two Towers.
It works fine in my view, provided you accept that in any opening act of a three-part story, the first part will only ever have an emotional climax rather than a plot-related one, and I think it's one heck of an emotional climax - Frodo and Sam's scene in the boat is one of the best of the trilogy IMO.