So, Sam Raimi is going to direct a Warcraft Movie

That should be "World of Warcraft Movie" but that would've made the title even longer.

Silver screen renditions of computer games do marginally better than P&P RPG to movie conversions (mostly because no-one tried that after the disastergasm that was Dungeons & Dragons) despite Uwe Boll doing his best to ruin the genre. Not many success stories exist outside the no-brainer (multiple meanings there, find them all) that was Tomb Raider.
Doom sucked except for the few minutes where it went FPS. Also suck does everything Uwe Boll made, especially his attempts at Bloodrayne and Dungeon Quest.
The rule of thumb seems pretty obvious. if you're going to take something from an interactive medium like a computer game and transfer it to the most passive all senses stimulating one, you'd better have something as interesting as Angelina Jolie in as little as possible tight fitting clothing for people to watch.

Book-to-movie conversions had a long and bumpy road before Hollywood got it as right as they'll get anything right. To the point where they manage to pull it off not to alienate everyone who ever read and liked the book but have most of them grudgingly admit the movie manages to capture some of the atmosphere, or even the spirit of the book. Of course, Hollywood's been perfecting this since, well the invention of movie theatres. Somewhere in between Book-to-movie and Game-to-movie, Hollywood's continuing mission to find new IP's to rape and exploit touched upon Comics. Since comics are already have a strong visual aspect to them and tend to be less big on annoying things like plot and thicker-than-cardboard characters, this ought to have been a marriage made in heaven. As it happens, Hollywood actually managed to only botch up about half of them financially and two out of three esthetically. A much higher rate of success than they got out of the world's literature.
With the advent of CGI over SFX and animatronics during the late 90's and early 00's especially Superhero comics have been making frequent appearances on the Silver screen with mixed results. From Fantastic Four and the Incredible Hulk to Iron Man and the X-Men series. The special effects extravaganza's manage to turn the hit/miss ratio into a better than 60% ratio. Sam Raimi's own contributions to the mix (Spiderman I- III) are amongst the better ones, possibly because he still cares about actors acting and stuff like emotions.
Computer Games being a more recent thing are still a bit of a moving target for Hollywood and what we mostly see is Hollywood's bussiness 'talent' moving into the Games industry rather than vice versa. Expertise is not flowing in the direction that would result into something I would consider great movies. It also goes a long way to explaining why Uwe Boll has been allowed to run free for the last decade. In fact, if you place Tomb Raider amongst the Super Hero movies, not that far a stretch of the imagination as the were shot as an Indiana Jones with Boobs movies, you could say that so far Computer Game to Movie conversions really have not scored at all, yet.

Of course, a Warcraft movie seems a safe bet. 3.5 Million fans in the us 4 in Europe, another 2-3 Million in China (and deprived of their WOW fix atm) should be a safe bet. Tombraider of course sold about ten times more copies over the length of its franchise, but if we were to count all (legal and illegal) copies of Warcraft, we'd get similar numbers. Numbers that all but guarantee a hit. Except that there is Doom. Doom isn't Half Life of course, but it's still one of the most played games in history, right after Civilization. Numbers alone don't do it. A decent director with a clear vision is also needed. They got that with Sam Raimi.

Sam has more to overcome besides the usual Computer Game to Movie issues though.
There's the protagonist problem. While most of us can't really identify with Lara Croft, very few really mind watching her vault and twist and squirm. Besides, watching Angelina's ass on tv with both hands free may have been an improvement for an audience used to having the time for brief glances of a pixelated derierre while dodging rolling boulders, wilde animals and whatnot. Doom in no small part flunked because the protagonist wasn't engaging us. Note that the FPS-like section of the movie is often lauded as the only fun part. It's a problem nearly any FPS game would have when being transferred to the silver screen. In the game the 'me' is you. In the movie the 'me' probably shouldn't be 'The Rock' as most people can't identify with him any more than with Lara Croft and he doesn't have the redeeming qualities Angelina Jolie has, (at least to the male part of the audience). In fact the Rock probably shouldn't be in any movie, period.
But that's beside the point I'm trying to make.

The point I'm trying to make is that MMORPG-to-Movie might have a similar hurdle to overcome as FPS-to-movie. Transplanting the protagonist from the player's 'me' to some kind of actor. It's easyto fall in the trap of thinking Star Wars and other movie IP's translated well to computer games didn't it, so what's the problem? Well, the problem is the messianic nature of Luke Skywalker. While the Star Wars movies and the Universe were so awesome that people wanted to experience adventures in and otherwise be part of that world that almost every computer game made from it did well. Of course, Star Wars is more the exception here than the rule. Nine out of ten Movie-games are best soon forgotten though usually financial successes.
Not many movie IP's transferred as succesfully to P&P RPG's, to computer games of every ilk from shooter to racing game to RPG game to comics, books and cartoons.

Ok, ok, ok! The point. I'm getting to it, honest. Movies by their nature tend to have a strong protagonistic presence. In both Scifi and Fantasy they're more often than not a kind of Everyman you're supposed to identify with. But with an MMO, much like with an FPS, if you played the game you already identify with someone. Your avatar. In the case of FPS'es you know what 'you' look like mostly from box art and loading screens rather than actual in-game visuals but in the case of an MMO you may have spent months collecting all the parts of the coolest outfit ever. Where cool is a very, very personal choice.
So how are you going to react to a Luke Skywalker on Azeroth? Is he going to stick out like a sore thumb with you not being able to identify with him at all, or will you be able to see it as 'just another fantasy flick' (meaning your expectations are very low and you'll likely end up being pleasantly surprised)?
Would it help if the main protagonist be not aimed to be something the target audience of 14 to 36 year old males so much identifies with as lusts after? I.e. a Blood Elf Jolie or Simpson? Or Megan Fox as a Night Elf or maybe a Tauren?
We don't always need to be able to identify with- or lust after our protagonist. Sometimes some kind of over the top, bigger than life version of a protagonist will do, as testified by the success of Silvester Stalone, Arnold Schwarzenegger and more recently vin Diesel have shown. While that worked for the Conan movies, the Rambo's and whatever vin Diesel did, would that work for a setting where there's a 'you' running around in it too? And what if the movie has him safe the day/world as is so common in the Super Hero / Scifi / Fantasy flicks of the last two decades?

I realize my audience doesn't hold many avid WOW players who will be confronted by this issue but I'll be interested in your take on this regardless.