Really to me it doesn't matter what the story is as long as it doesn't get into the way of the Metroid core (to me that's Veni, Vidi Vici, exploring, understanding, dominating, gaining familiarity with the environment and more abilities to better handle it). The Metroid core is not exclusive to Metroid, it's just what I buy Metroid for. To me Castlevania (SotN - DoS, I think PoR and OoE just did it wrong) is Metroid. Bunnie Must Die is Metroid. Shadow Complex is Metroid. Metroid Prime is Metroid. Metroid Fusion is NOT Metroid. Fusion is a game for people who cannot handle the Metroid core to be mislead to believe that they are playing a Metroid game. After all it has Samus, it has Metroids, it has a connected map, etc, right? That's all just window dressing around the Metroid core. Metroid Prime 3 is pretty close to not being Metroid too. I'm a bit undecided on Hunters but overall it still felt like Metroid, even if it was a fairly weak Metroid.
My real problem with Other M is that Sakamoto stated that it will be like Fusion. Fusion is not what I want when I buy Metroid. If they want to make something that's not Metroid then why do they call it Metroid? Why not make some kind of new IP that can be about whatever you want and isn't tied to 8-bit era character designs to boot? Nobody would object if this was a game about a different future girl in power armor. She could be as emo as they want her to be, nobody would expect otherwise. They could make the game into a corridor shooter with ninja moves and nobody would mind. But they called it Metroid so they better damn well deliver Metroid.
Honestly, I think there's probably very little really good voice acting out there, so this isn't that bad relative to the norm. I have to turn English voices off on nearly every anime I watch.
We aren't comparing it to shitty anime dubs, the standards for the next big game in a major franchise should be higher than those of a niche cartoon that was localized straight to DVD.