Not to offend, but I am a big time anime fan, yet I find most anime's based on video games to be VERY disappointing…
Parappa the rapper: A prime example... There was no rapping, he didn't once say "I GOTTA BELIEVE!" Pj became more emotionless, and Lammy was not in it AT ALL (thought I will not lie about one thing, I did like the opening theme and Ending theme)
Pokemon: As much as I like the pokemon game series, I must admit the anime lost my interest some time ago (until May appeared, damn you Japan, using fan service to lure us horney fanboys >.>) it's so damn REPETIVE! It's like a pattern to all the eps, making it as predictable as possible (Thought I will not lie, I do still watch the movies since they actually put effort into writing those)
Veiwtiful Joe: I've never played the game, but I expected better from the anime... the anime goes by WAAAY too slowly and when the action starts it's not anything speical or cool like the games >.>
Sonic X: It started out okay, but all the damn human characters killed the stinkin plot >.> I've heard season 2 is much better... I've never seen it, but I would not mind giving it a try...
Megaman NT warrior: I know it's originally called "Megaman EXE." and I am aware that the dub was tampered with alot, but frankly this anime got old for me fast... I admit it did have a fine start, but I lost interest in it before the first season even finished... In the words of Parappa: "At first... I liked it... but now I don't even wanna look at it..."
Bomberman Jetters: Never seen it, but I like to give anime chances... and chances are this one might be as disappointing as the others I mentioned >.> I'd still watch it so I could give a fair opinion though...