lol a part of me doubts that even Mario and Peach totally love each other. I mean, he saves her sorry butt every game (and she saved his once) and they don't ever do it at the end of the game (or get married, whatever floats your boat). Let's face it, Peach only likes Mario 'cause he gets her out of trouble; once he's done that, she has no more use for him. Either the window of opportunity closes after he saves her or it ain't ever been open.
I guess what I'm trying to say here is that love isn't and should never be a big theme in Mario games, especially since plot has only been fully used in games like Mario RPG, Paper Mario, etc.