No matter how you slice it, FF is a series that caters to people who like graphics and plot. So SquareEnix was practically forced to put FFXIII on the HD consoles because most of their fans were expecting the graphics to be near the best of this generation. If it was on the Wii, many fans would have skipped the game in protest or just bought FFXIV instead, purely based on the graphics. It sounds bad when you say it, but deep down many people even here know that a large part of what you've come to expect from the series is a vast upgrade in visuals and that 'wow' factor from each title. And you would have been protesting from day 1 the game if it was announced for Wii because you would have felt they couldn't deliver that.
That said, obviously other series can go to Wii and do just fine. The most obvious example is FF sister Series Dragon Quest, which is already doing this. But that game has never made graphics a primary focus.
Six upcoming games you should look into:
