Because I like "simulation" games or similar, I prefer regular sized. My imagination isn't good enough to suspend reality to that extent. Same with ginormous tits.
Average to a little over average is fine. Massive coke can foot and a half long dicks are just so unrealistic that it's difficult to really get into the scenes.
I don't really care mostly. That said there is a point where it either becomes cartoonishly big and looks dumb or small enough to where it takes me out of the game