Plunderland

Plunderland is a side-scrolling game, like early Sonic or Mario titles, that always keeps you moving forward. The premise is pretty basic: Sail from port to port, pillaging as you go, battling the English army, sharks, sea monsters, and (if you choose to engage them) island natives. It's simple to learn, graphically appealing, and lets players interact with the environment to an impressive degree (much like Pocket God). That interaction helps to keep the game fresh and adds to the replay value. It also plays into the strategy of the game (i.e. do you use your own ammo or catch shots from enemy ships mid air and hurl them back to where they came?). But, in the long run, the sadistic potential of that interaction (drowning or burning your opponents) makes it a questionable title for younger players.