"Since when has there been a large launch(in terms of numbers of games) for any Nintendo console? Never..."
SNES. Super Mario World, F-Zero, Pilotwings, Sim City, Super Ghouls 'n' Ghosts, Act Raiser, Gradius III, etc. I think Final Fantasy II was even a launch title or at least was close enough. The amount of great games released for that console in 1991 was insane.
And the amount of great titles isn't significant. What's important is that the flagship title be a system seller. As well as Luigi's Mansion sold, few thought it was worth owning a Cube for and it failed to keep up interest for the six month game drought that followed. Nintendo should have launched the Cube with Super Mario Sunshine.
Let's put it this way, when people who just bought a Cube ask what game they should get does anyone suggest Luigi's Mansion?