There are plenty of amazing platform shooters out there. Metroid. Gunstar. Contra. None of these games can quite compare to Cave Story, though.
Released in late 2004, Cave Story harkens back to a simpler time. The graphics are 8-bit, and yet they manage to be beautiful. The music consists entirely of chiptunes, and yet it's some of the best composed video game music I've ever listened to. And the gameplay? Fantastic.
Cave Story starts in, well, a cave. Your character wakes up with no memory of who, or where, he is. He is completely defenseless. Soon, however, he acquires a weapon, and that's where the fun begins. As the game progresses, you can collect up to five different weapons from a pool of nine.
After leaving the cave, you soon learn that you are a soldier robot sent to a floating island in the sky (the game's setting) almost ten years ago. Your character's true history, however, remains a secret for almost the entire game.
The graphics in Cave Story were meticulously crafted, and are very attractive despite their simplicity. The music is similar in this regard. Coupled with an extremely engaging story, these factors make Cave Story one of the finest games around. It's no surprise it took the creator, Pixel, almost five years to make.
Do yourself a favor and download it today.
Note: Cave Story (aka Doukutsu Monogatari) is a dojin (sometimes spelled doujin) game--that is, one of a genre of Japanese games created by non-professionals. The "delux" package for PCs includes an English translation patch and a game guide; to play on the Mac, you'll need to download both the Mac version and also the English language patch for Macs. (Unless you read Japanese, of course.)