While it may have copied Smash Bros, it still sounds amazing. My ideas for

Stages:

BUZZ!! - You can grab an in-game controller, answering answers correctly gives you health, answering incorrectly lowers your health.

Littlebigplanet - Similar to the Warioware stage, It randomly takes you to popular mini-games in LBP2, such as "Clockwerx 2"

Cheatau (something like that) remember in the Uncharted 3 level 6 where youre in a burning building? Yeah that one.

Graveyard Ship - In Uncharted 3, this level was my least favorite. However, it could be cool for this game.

Airfield - that multiplayer map in UC3, the starting part would be awesome IMO.

The Sewers - From Infamous.

Something from Sly Cooper where you have to hide when the lights are on, otherwise you get hurt. You have to attack when the lights are out.

A Sly Cooper level where you are being chased by Carmelita

A Wipeout level similar to the Mario Kart level.

A Heavy Rain level involving Quick time events.

Your ideas?