I really liked the Warcraft movie. I went in with super low expectations and walked away pleasantly surprised.
I think that anyone who likes fantasy could go see the movie and enjoy it, even though fans of Warcraft will feel more familiar with the world and setting. Think of it like Lord of the Rings, if you were a book reader and went to see the movies when they came out you would get more out of them. Same idea here if you've ever been a Warcraft player.
It seems like it's broken records in China for ticket sales so I'm hoping we'll actually get to see a sequel or two. I bet this could be better as a series than as a stand alone movie.