The only game this theory holds up for is the legend of Zelda. For singleplayer only games the others aren't particularly long, especially when compared to titles like Demon's Souls on the PS3, and Demon's Souls is a fair bit longer than Zelda.
In my household, most the Wii titles we have are third party, and they generally consume more time for singleplayer playthroughs too.
Plus of course you don't take into account multiplayer... well in a sense you do... like with Mario Kart. I don't see the point in playing Mario Kart for months unless you're going to be playing multiplayer, in which case you should realise that the lifespans on 360/PS3 games are in fact much, much longer due to additional multiplayer content.
I'd even go as far to argue that typically multiplayer only games like MAG will get much, much more playtime than Singleplayer first party Nintendo titles.
It's because Wii is for casuals and casuals don't research purchases, and make them on the basis of brand recognition and whatnot, little more.







