Faxonboy,

I think it might be helpful to remember that your ordinary waking-life experience is a cartoon-like construct informed by sensory information, not a direct experience of your environment. We often draw conclusions about how 'real' an experience is based on how vivid it is, but those conclusions start to fail when we start dreaming vividly. Even if you were privy to events in a parallel world, your mental dream-story about this would still be 'imagined', even if 'real' information is incorporated into it.

As I see it, our physical world has a kind of coherence to it, a way that it works. Our imagined worlds usually fall short of that kind of coherence - they break down if you analyze them persistently enough. They have a sort of pseudo-reality in that they're connected to our thoughts, and sometimes have the potential become real in limited ways. But they're not actual other-places in the same way that the physical world is.