Princess Mononoke is right up there with Akira as my favourite Anime film. It just does everything right and is still as enjoyable now as it was when I first saw it some twenty odd years ago.
Although the film is called Princess Mononoke its more about a dashing prince called Ashitaka and his journey to remove a curse that befalls him. This brings him in to contact with various groups of people (including talking Wolves and a Forest God) who all have their own ideas/agendas, whereas, Ashitaka just wants everyone to get along.
The animation is superb, especially since it was made in 1997, and the imaginative story is very relevant for Today due to its strong messages around nature against technology and everyone living together. There is also a top-notch dub cast with people like Billy Bob Thornton and Minnie Driver involved.
I must also mention the superb soundtrack which really captures the uniqueness of the film mixed with some great action tracks (there is even a specific symphony version available if you can find it).
Note that Princess Mononoke slightly confused my daughter as there were no definite good or bad people. She was also a bit freaked out by the wood spirits.
Verdict: The best Studio Ghibli film ever and quite possibly the best Anime ever. A must watch if you are brave enough to try something a bit different.