I think some of this might have to do with getting games approved for a disc. On wii, it is much easier to get your game approved by Nintendo for disc pressing than Sony and MS. I'm pretty sure the HD systems have requirements on the size of the game, and if it doesn't hit a certain size it becomes DLC.
New Super Mario, Kirby's Epic Yarn, DKC Returns; they are all great games, but can't be more than a couple hundred MB of data. They just re-use so many objects and the graphics are only marginally better than similar games which fit on a DS cart. In order for a 2D platformer to be non-DLC it has to be something as amazing as LBP or LBP2.
I don't really want to get into the 'casual' argument, but $50 or $60 for a 2D platformer is too much IMO for those Wii games when I can get Halo, COD, Fallout, etc. games for the same price. You have to know that way less development time went into those 2D games. Keep all those games as DLC unless it's something phenomenal (LBP) or aimed towards kids and discounted (Kung Fu Panda).
