Voice actors are more than just minor celebrities: they are so essential to a character that they become inseparable.
Like with Japanese gaming, Western gaming has characters that cannot be separated from their voice actor. Take David Hayter, for example, the English-language voice of Metal Gear Solid's Snake. Or Nolan North, the voice of Uncharted's Nathan Drake. Or Charles Martinet, the voice of Mario.
But as more and more Hollywood actors make in-roads into video game voice acting, it becomes less about the voice and more about star power.
Voice actors achieve minor celebrity status in Japan. Some voice actors cross over in to Japanese pop or even make their way to live-action television. For those who stay in voice acting, there are dedicated magazines that feature interviews and photo layouts with vocal talent.
The voice itself is of the utmost importance. It's no wonder that when Square Enix was unable to secure Kouhei Takeda, who voiced Vaan in Final Fantasy XII, the company considered canceling the character's appearance in Dissidia 012 Final Fantasy. But fan interest in Vaan remained high, so Square Enix decided to put the character in the game, but with a new voice actor.
Kensho Ono, who voices Harry Potter in the Japanese dubs and most recently Andy in Toy Story 3, will take Takeda's place. Since the Harry Potter movies and Toy Story 3 are viewed by younger Japanese moviegoers, the dubbing is incredibly important. The importance of Ono's performance is increased ten fold. For many Japanese, he is the voice of Harry Potter. And he is a talented voice actor, but he's not Takeda. Diehard Final Fantasy fans will notice the difference, but everyone else will just be happy to have Vaan.
All character have an essence. The reason why some voice actors become closely identified with certain characters is that they find said essence. That doesn't mean only one voice actor can voice a character. The most famous video game characters will outlive us all. It's up to subsequent actors to latch on to whatever makes those characters tick and bring them to life.
Dissidia 012 [Official Site]