Melee's Game Over screen really was a little haunting, especially with that deep "Game Over" voice from the announcer. Brawl's normal screen took away the trophy of your character (at least outside of Adventure Mode), but the music kept it a little scary still.
The music was a little happier in Brawl's Game Over than Melee's, though.
Melee Game Over Screen
But if your trophy shattered at Game Over... I'm not sure the kids would be too happy to die, then. But it would really add to the "haunting" appeal of such screens.
But agreed. Brawl and Melee sometimes took themselves a little seriously. Sakurai can add a little humor to Adventure Mode as well as other parts of the game next time. Maybe Victini attempts to attack some other character in a SSE-type Adventure Mode, but lights his ally Luigi's pants on fire instead by accident. That sort of occasional humor help keeps the game for getting too serious over itself.