People keep lumping games into "hardcore" and "casual" groups, why not look at it from other angles?
Take a look at what games sell on the HD consoles (the 360 especially). You'll notice that unrealistic Japanese games haven't really proven they can sell (far less than core Wii games anyway). All of the best selling games put heavy stress on realism. Take a look at the best selling RPG - Lost Odyssey. Not a surprise, as its art style is perfectly fit for the western audience. Compare its sales to Blue Dragon, Tales of Vesperia, Valkyria Chronicles, etc.
Now, look at the games that feature cartoony characters, or take the stylish route - they don't tend to sell nearly as well. The million sellers are Viva Pinata (bundled), Ratchet & Clank, Lego Indy/Kung Fu Panda (bundled), LBP, and Lego Star Wars. Note these are all western games, the Japanese games sell far less. The Wii is pretty much the opposite of this. For example, Sonic games sell best on the Wii, outpacing both HD consoles combined.
So, for anyone that's using the "core games aren't proven Wii argument," there's also a "cartoony/stylish, unrealistic games aren't proven on HD consoles" one.
Btw, America is KH's strongest region by far, seeing over 55% of sales there. This alone means making KH3 exclusive for the PS3 would be an extremely foolish move.
