What exclusive games on each console family do you think would sell more systems if rival consoles could sample demos.
Fire Emblem seems like something that attracts a crowd that might overlap Sony's stereotypical fan (though thankfully we Nintendo fans are coping on to this gem in plain sights, certainly took me a while).
Knowing that different the companies attract different hardcore niches what high quality games but under valued exclusives would you find it interesting to give different fanbases a demo of.
Remember your goal would be to increase the games profile and win console converts, Zelda, Mario, Halo, Uncharted, etc don't count.
CLARIFYING EDIT: I mean to ask what games could suddenly become system sellers if one of the rival crowds really knew of them.