Video games based on Japanese animations are a dime a dozen these days, with iterations upon iterations of Dragon Ball Z, One Piece, Shonen Jump, Bleach, Dynasty Warriors: Gundam, and Naruto Ultimate Ninja Storm Oh My God There Are Too Many Words In This. Most of these titles aspire to be nothing more than annualized fodder that sells well, is relatively inexpensive to produce, and bring awareness to the brand, if nothing else. They're cash-ins through and through.
What about the opposite? Well, it's pretty much the same deal: Japanese animations based on video games usually don't fare well, either. They don't get a huge budget, are restricted by a strict deadline, and suffer in both story and production quality as a result. At the very least, we don't have to deal with Uwe Boll's gut-wrenchingly awful film adaptations of Resident Evil (and everything else he touches).
But that doesn't mean there aren't heaps of stinking Japanese animations that ruin the magic of the original video game, like Blue Dragon, the Chrono Trigger comedy, the Americanized version of Darkstalkers, and the blasphemous artwork of the Tekken OAV. No really, if you want to watch something that will make you appreciate everything else on the planet that much more, suffer through the Tekken OAV. It actually makes the Tekken 2010 live-action film tolerable.
Luckily, there are twenty animes based on video games that don't suck, twenty gems in the sea of muddy animations that shine as beacons of how to adapt a video game franchise properly. Some of these are straight-up action films that don't care about story and some are subtle, character-driven dramas that don't care about action. Either way, they prove that there's hope in the animated universe. (Also: a shout-out to the Japanese live-action film for Phoenix Wright. Just about the best theatrical film for a video game I've ever seen.)