The Last Airbender movie was a travesty wrapped in a disgrace and lightly dipped in sham. 1/10
The Transformers movies, in the best way I've ever heard it put, are enjoyable in a "Turn off your brain, don't think about the plot, just watch giant CGI robots punch the **** out of each other" sense. I'd say 3/10
Speaking from a film studies/writing degree perspective, adapting manga, anime, or video games to the silver screen is one hell of a task. By far the biggest reason for this is because you have two entirely different audience demographics that need to be catered to; the fans of whatever you're adapting, who will know the original subject matter front to back, back to front, inside out, and sideways, and people who have never experienced the story but will be attracted by your previews and advertising. That, by itself, presents a large roadblock because you must stay true enough to the original to satisfy the former group while bringing the story close enough to more conventional storytelling and techniques so the latter doesn't get lost, all while making sure your vision as director/producer is clearly brought forward.
The second largest difficulty is the nature of the mediums involved. Anime & manga are both episodic, with a through-line of plot and ongoing action that persists week to week, month to month, and each episode or chapter has its own moderately contained mini-story that builds the overarcing plot. This is what allows those mediums to tell these big, sweeping, long-term stories and focus on as many of the small events between Point A and Point B as they do, when done well. That's how Death Note allows us to see Light's thought process and personal conflict in the sizable majority of his killings and his scheming, or how in a big bad Warring Kingdoms story like Avatar: The Last Airbender we get to follow all the little stops, events, and lessons Aang and company learn between destinations (or how in Lord Marksman & Vanadis we get to witness the strategy and unfolding of almost every battle)- the nature of the beast gives the creator(s) the time and breathing room needed to focus on the microdetails. On the other hand, movies and novels (which are the more common and far more successful/easy adaptation target) are all about the macro; you as creator have 100-140 minutes or 250-400 pages to introduce your protagonist, take them on an adventure, get to the point, and wrap it up with a neat little bow or a cliffhanging sequel hook. You don't have time to focus on every little thing that happens between the Innocent Country Village and the Caves of Despair, you just hit the ones that have a major impact on the plot and keep it moving.
So, when you try to adapt an episodic story to the straight shot, hit the high points medium like film, you inevitably cut things out, which fragments the story and requires rewriting to cover the holes... which can easily lose the non-fan in the details and inevitably enrages the fan because you changed something or cut their favorite side bit. And even in a case like the Last Airbender movie, where whether or not someone enjoyed it depended almost entirely on whether or not they had watched the show, at best that will break your audience base in two roughly equal pieces, which is almost guaranteed to sink your ratings.
As for video games... I think adapting them to film is something that simply cannot work. Part of what makes video games appealing is the immersion; even in a heavily pre-scripted story like Final Fantasy or Legend of Zelda, 90% of the events of the plot are triggered or influenced by characters directly controlled by the player. And that is a powerful feeling, so much so that one of the aspects that will gain a game a lot of prestige is finding a new way to work it. Assassin's Creed as a series took off in part because they did just that with the second layer and the syncronization, and one of the fundamental building blocks of the Bioshock series is that the games offer the player a choice at several intervals, and by doing that they bring player and character that much closer. Even if there is enough of a lore to a game to make a movie out of it, which there are plenty of games that have such, by adapting it to film you are required to completely remove that immersion, which means that no matter how faithfully you stick to the story the audience will always feel that something is missing.
Anyway, those are my two cents as someone who studies/has studied film and writing, feel free to take what you will. I can only hope it helped.
Edited by Hero of Ishval, 01 July 2016 - 02:33 AM.