Notgames don't exist.
Notgames is simply an invitation to design interactive or procedural content without game rules.
But I love screensavers!
Our first published game, The Endless Forest, was -and still is- a screensaver. And it's very interactive!
I guess screensavers are designed without any attention to game conventions. So maybe they are a good example to guide us.
Some types of content simply don't require interaction. Though, in general, I'd think it's rather wasteful to create a real-time piece an not implement some interaction, given how powerful it can be towards expressing your content. A virtual aquarium becomes a lot more convincing when it allows you to tick on the glass to chase away or lure the fish.