Actually you'll recognize quite a few game characters are already modeled after Gackt. Most are from Square/ Square Enix Games Such as Final Fantasy and The Bouncer. The creator,Tetsuya Nomura, has even stated Gackt is one of his favorite artists and so he uses him for alot of his characters looks. Here's some links below for comparison.<br>
Most are not confirmed definite he was the model for it but c'mon most pix look waaaay too much alike to be coincidence lol

Squall Leonhart from Final Fantasy VIII (8)
Squall One<br> Squall Two<br>Squall Three<br>Squall Four<br>Squall Five<br>

Cloud Strife from Final Fantasy Advent Children
Cloud One
Cloud Two<br>Cloud Three<br>

Tidus from Final Fantasy X (10)
Tidus One<br>

Final Fantasy XI (11)
One<br>

Dauragon from The Bouncer
One<br>

Kenshin
One<br>
Alucard from Castlevania
One