I don't get this hate for the r-word. I hardly dare even type it, it's come this far. 
First of all, I don't think that four bisexuals are unrealistic. Or eight. Or whatever. Also, no game will ever be fully realistic.
But a game can attempt to *approach* realism.
If, in a shooter game, an enemy goes down after, say, one or two hits with a 7.62 battle rifle, then that is relatively realistic within the parameters of a video game.
If the same enemy can eat an entire 20 round magazine of the same type of ammo, then that is relatively unrealistic.
Arguments like "you can't romance everyone because there are only four LIs in the game" are deliberately picking a level of realism that, in absence of unlimited time and resources, a game can never achieve anyway, and from that you conclude that there's no need to even attempt to approach realism in any other aspect.