Why can't Wii Ware games be bigger?

[Soma]

It's also a good way to experiment and create new ideas. Bigger games cost more and companies risk less. With low budget games they can try to create, in Iwata's words, "a new Tetris", which wouldn't be possible with high budgets.

Also, some Snes, N64 games were of less size and still offered long periods of gameplay and replayability.