Fact: There were a lot of games for the NES. Like easily over half a thousand.
Theory: Most people will never get a chance to see, much less play every NES game ever made.
Hypothesis: If there were a way to view multiple NES games simultaneously, then it would be easier to for someone to randomly play one.
Conclusion: Someone should make a screensaver that displays multiple NES games in progress and let you jump into one at any time.
What your looking at is M \ K Productions NES Screensaver, which displays a combination in-game demo modes with emulator-recorded movies to create a wall of clips from NES games. At any time you can click on one of the tiles and start playing the game in an emulator (specifically UberNES, which was made by the same people).
Of course, some of you out there might be thinking, "this seems interesting, but what use is it to me? A fine, upstanding individual who would never even consider downloading a ROM file." Well, speaking as a fine, upstanding individual who would never even consider downloading a ROM file myself, I can say that this screensaver can still be used without infringing on anyone's intellectual property.
The only thing the screensaver really requires to work are UberNES movies, which by themselves are not illegal. Said movies can be downloaded from the emulator's movie gallery and contains enough unique footage for two full days of play.
Sure, this won't allow you to actually play the NES games through the screensaver, but those are the sacrifices one has to make as a fine, upstanding individual.
Uber NES Nintendo Screen Saver via GameSetWatch