Upon the advice of people in this thread, I downloaded and started playing Cave Story this weekend. All I can say is: wow. This is quite possibly the greatsest NES game that never was. It is ridiculously fun in a very classic, very old-school way.

The boss fights are difficult without being impossible. The save points remove the stupid difficulty of old NES games that required you to memorize every level - but the challenge level is still there. The gameplay has just been polished to perfection to such a degree that it gleams like the precious gem it is.

Makes me almost wish I had a Wii so that I could get it and see what extra features are being put in the game.