Devon: By your own argument, only the "main series" games count. That was, after all, the basis you used for claiming KH to be a "Sony Exclusive".
Anyway, I thought I'd suggest a few more cool ideas for crossovers.
Ice Climbers x Pikmin (hey, maybe Popo and Nana are related to Olimar...)
Mario Party x Rabbids
Star Fox (as per Adventures) x Rayman
Paper Mario x Alex Kidd
F-Zero x Excite
Metroid Prime x The Conduit
Kirby x Pacman
Pokemon x Resident Evil (hey, Umbrella would probably like using pokemon like Cofagrigus, Shedinja, Gengar, and Darkrai)
Star Fox x Fantasy Zone