Seriously, many of these so-called "Rivals" aren't rivals at all, but downright enemies!
Like, Red & Blue from Pokemon are rivals, but Link & Ganon?! Mario & Bowser?! Megaman & Dr. Wily?! THESE ARE NOT RIVALS!!!
http://en.wikipedia.org/wiki/Rival
A rival is a person, team, company, or other organization competing against another person or team, etc.
Most of the people in this contest aren't competing with each other...Not really. Most of them are straight up enemies.
Take the 3 I mentioned earlier, none of these "rivals" are actually competing with each other for a common goal. Ganon, Bowser, and Wily are just trying to seize control of their respective worlds, and Link, Mario, and MegaMan are trying to stop them because they're heroes.
Red & Blue ARE rivals, because they ARE both competing for the same thing, to complete their PokeDex and become Pokemon Legue Champion.
I know I'm nitpicking, but really... Why did they call it "Rivalry Rumble" when only like 10% (if that) of the characters in it are actually rivals.
--
I imagine Bethesda's Quality Testing Department a big, dusty room filled with cobwebs, and a chimp wearing a Fez banging on the keyboard of a single computer...