Okay, 20 times I decided to play this and keep score. One point for him if he guessed it on first try, half a point each if he failed before he got it right, a point for me if he failed altogether; limiting my choices to fictional characters or real people who are known well enough.
Round one: Akinator 1-0 Vegosiux
He guessed Viconia.
Round two: Akinator 1.5-0.5 Vegosiux
He guessed the Overlord, after failing once.
Round three: Akinator 1.5-1.5 Vegosiux
He didn't guess Coach Oleander.
Round four: Akinator 2-2 Vegosiux
He guessed Anze Kopitar, after failing once.
Stumped him first time with Saavedro, the main antagonist of the third Myst game (Exile) xD. I'm good at this ;D
EDIT: Tried again with the characters Ullii and Karan from the Three Worlds Cycle (novel series), and also a Spartan from the Halo books - Lucy-B091. He didn't guess any of them correctly, though came close with Lucy (guessing a different female Spartan, Kelly).