Chomp
A maze, pellets, power pellets and four ghosts, with its own score, clock and music.
The marble keeps rolling, but the world stops letting it roll anywhere. Chomp supplies its own maze, its own pellets and power pellets, its own four ghosts with scatter and chase behaviour, its own score, and its own music.
It has a real ending, which is the part that matters architecturally: clear the maze or run out the clock, and either way it resolves and restarts on its own rather than waiting for someone to build the plumbing around it.
That makes it the second release candidate, and the one that proves a mode can own the rules without owning the game.