Well, if I had to choose myself, I'd suggest the Breakout. The reason I say that is; you can use most of what you learned in doing the Pong example, even to the point of sharing a lot of the same code, only now your targets are removable bricks of dirrent point values.
Then I'd add some embelishments to the Breakout, like falling bonuses and multiple balls, lasers, capture and all that fun stuff.
Once you get past that, go in for the Pac-Man, where you need to build an AI for the ghosts to chase the player around the screen, or run away when the player eats the power cookie. As Zen says in the other thread here--one step at a time....
S.
Any truly great code should be indisguishable from magic.