If you've ever written computer code, you'll know 60 MB is a hell of a lot. For a game that draws 2D pixels and has a few directional controls, it's insane. There's clearly something being added into the game that bloats it with stuff that contributes nothing to the actual game. eg. A generalised full-function 3D engine that's being used in a simple way, or a load of Sony libraries to enable leaderboards pr something-or-other that are mammoth.
It wasn't an attempt at an exact figure. The point is the game is far, far, far bigger than it ought to be based on what's required to draw 2D, 8 colour sprites at 160x120 resolution or whatever it is.
Ahhh, that explains it. The PS3 version comes with a complete Wii emulator!