I've never played Far Cry the game, so I can't say how faithful Uwe Boll's adaptation is. But I will say that it's terrible. Really, really terrible.
How terrible? Well, I'll assume by the credits stating "music by _______" that this is unfinished (or possibly that no composer was willing to be openly associated with it), so for now I'll ignore the abysmal editing and the bizarre two-second inclusion of The Usual Suspects score. Perhaps this is just an early cut.
But the dialogue. My god, the dialogue. It's so unabashedly awful, it can't even follow the conventions of bad dialogue. Woman says, "You're a sick, egotistical maniac!" The bad dialogue rulebook dictates the madman's smug, calm reply should be something like, "I'm not that sick," or, "You forgot sadistic." But come on, "Let's not go over the top"? That's all you have to say? If you're going to write something this bad, at least make it less boring.
As far as the first line being spoken in a thick lisp, and the seemingly-post-coital erection joke, I have no idea.