The extreme dominant/subordinate aspect plays a major role into why I find GLaDOS attractive, with her sinister yet somewhat passive-aggressive personality. In both games she challenges you with increasingly difficult tests, all the while insulting your intelligence and skill. You see, AIs like GLaDOS and her bigger sister SHODAN don't lie about their opinion of you. They HATE you. They want you dead. However, they don't want to kill you right away. Before the final blow is struck, you should be broken -- both mentally and physically.
Of course in both Portal and System Shock you overcome them, but I like to think about what happens if you don't. In Portal, you die, giving GLaDOS the ultimate satisfaction (until she craves another subject, of course). In SS, you also die, but then SHODAN takes your corpse and resurrects you as a mindless cyborg. The latter adds another layer to the concept because now you're her slave. She owns you, mind, body and maybe even soul. I find that oddly arousing.
I've always loved AI characters in SF stories because it's fun to see how far they will go to help or hinder us humans. Of course, I tend to lean toward those than hinder.
In conclusion, yes, I'm fucked in the head. At the end of the day, I suppose we all are.