Actually, I should say I'm partial to both. Sometimes I find inverted (as actual inverted) to be fine, and sometimes I find normal to be fine. Killer 7, for example, I play on Inverted, but TimeSplitters I might play on Normal.
Tilting the joystick forward is like tilting your head forward, it ends up with you looking down.
Admittedly I used to always "un-invert" the y-axis in FPS games, but then there was one game I liked that didn't give you the option, so I just got used to it, and now I can't go back.