So, video game movie adaptations are basically guaranteed not to be good movies. There was a lot of hope for Warcraft to change this trend, employing a popular up-and-coming director and adapting a series that I'd wager is a bit more popular than, say, Silent Hill.
Sadly, I don't think that this really changes the trend - but not for lack of trying.
Warcraft, the film, roughly adapts the events of the First War. A lot of the elements we're familiar with are in play, along with some adjustments that came to the lore after the first game.
One of the challenges to the film of course is that they need to condense a ton of lore into something that can be digested as a film. So we have, for example, Grom Hellscream show up in a bunch of battles, but we never hear him say a word because frankly there isn't enough room for him as a character. We also see the Draenor-side of the Dark Portal being opened using the life energy of caged Draenei, but the Draenei are never identified by name and the movie doesn't spend any time on them - and that's for the best. World building is all well and good (I'd consider it one of the main appeals to fantasy) but movies have a very limited time to tell their stories.
Visually, it's a mixed bag. I think the Orcs wind up looking pretty decent, though one wonders what a fully-animated film might have been like. The fact that CGI Orcs are interacting with live-action actors really draws attention to the CGI nature, which is a shame because I do think they put in a lot of effort to make the orcs look good.
The art design goes a bit too shiny for the Human stuff if you as me - I get that it's trying to represent the look of the game world, but I think we were all expecting more of a Minas Tirith in the Lord of the Rings movies feel. This is a bit, well, Disneyland.
Most of this stuff I'd forgive, but the biggest problem the movie has is that the characters don't really do much with what they've got. There's one big exception: Ben Foster as Medivh plays him not only as the powerful wizard who is secretly corrupted by demons, but also brings a kind of world-weary sarcasm to it. He is introduced wearing not his classic raven-feather robes, but shirtless and working on a giant golem. He seems more like an eccentric artist guy you might know who has a history of drug problems and has probably been through a lot more bad stuff than he's told you about.
But unfortunately, no one else really finds much to do with their characters. Anduin Lothar is the dutiful hero, Llane the calm and reasonable king. Khadgar is given some weird backstory about having been given to the Kirin Tor as a child and then running away but still practicing magic. Durotan is the One Sane Man in the Horde, though he only ever seems to convince Orgrim (sort of.) Gul'dan is just nasty and evil, but that's appropriate.
Still, I'd say that if you just want to eat some popcorn and have fun spotting the more obscure references (some people ride past a dungeon meeting stone at one point,) the movie is perfectly adequate. This isn't going to be getting a Criterion edition any time soon (then again, Armageddon did) but if you just want to see some crazy fantasy action, it's worth a watch.
My advice for lore-sticklers though - don't worry too much about specifics. With one exception, most of the significant developments from the First War are accounted for. I do wonder, if they were to make more movies, if they could even get to the Third War. I personally think the story of Arthas is one of the most compelling things they've done in Warcraft and I'd really enjoy seeing it on screen (even flawed like this movie was,) but I don't know how likely that is, as there's still a lot of ground to cover and I don't know how eager they are to make more of these.