The Monkey King is a big uneven mess where low points are interchanged with some real high ones but where it requires some effort to get rewarded fully.
You have to sit through some slow and agonizing first half hour before the (minimal) story gets rolling. However it takes an hour extra to really get to the good stuff. Problem with The Monkey King is that doesn't explain the mythology that well. You get introduced to all these deities and spirits where it is assumed that you know about them. I haven't read Journey to the West. Although I am familiar with some other adaptations like the ones featuring Stephen Chow (which are brilliant BTW). And of course Dragonball (anime). But those deviated from the source material quite a lot so those aren't that helpful. Seeing how this film is setup as the first in a trilogy, you would expect for them to explain a little more than they did. Sometimes you really wonder what is going on and why things are happening the way they do. Then I stopped worrying about that and just followed Donnie Yen as Sun Wukong (Monkey King) and his antics. Donnie Yen is quite phenomenal. He truly moves like a monkey would and above that he is able to act with his eyes since everything else is covered up with costumes and makeup. At one point it becomes quite clear of what is going on and from that moment you are treated with a lot of spectacle. Which brings me to the special effects. On the one hand you have some truly wonderful visuals and on the other the CGI is so bad that it becomes laughable. More so when instead of CGI you get to see people with some horrid looking masks portray animals that look far too fake to accept and overlook. You would expect this in a low budget film. Not in a box office hit as this one. However in the last half hour the special effects and visuals are consistent and impressive. In these last thirty minutes we finally to get to see The Monkey King realizing that he has made some mistakes and tries real hard to correct them. For me that was quit the highlight. And just when I was prepared for more the film ends just a tiny bit abruptly. Although it does seem to be a fitting end to the tale. When I was watching this I was not aware for the plans for the trilogy. But now I kinda look forward to that. The sequel however won't star Donnie Yen but Aaron Kwok as Sun Wukong who strangely enough starred as the Bull Demon King in this first part. (In case you were wondering, Donnie Yen is not returning due to his commitment to Ip Man 3. Which is very good news if you ask me.)
For the most part The Monkey King is a fantastic tale filled with wonderful action and nice visuals and there is enough (for me at least) to be looking forward to the sequels. But keep in mind that this film is a family movie and made to appeal to children. So a lot of is toned down.