A poor localization of a video game will force Western voice actors to deliver stilted, awkward lines that resonate poorly with the audience.

It can be difficult to work with material that comes from another country and adapt it to a point that makes sense for Western audiences; additionally, the localization process does not usually make hard changes to a game, and voice acting will have limitations because of that. For example, a cleverly delivered scene in Japanese with quick comebacks may sound awkward in English because the same intentions cannot expressed so quickly.

You may find that you have less of an issue with Western voice actors if you watch animated series or video games that were produced in English first. Would you say that Batman: The Animated Series or Gargoyles had poor voice acting? I certainly would not.