This is getting philosophical fast.
Here's my take. There is physical reality, and there is perception. You form a mental model of reality through perception. This is what people are trying to say when they say everyone has their own reality. I think that's a bad and misleading way to put it, because it implies that perception and reality are the same thing.
For example: a given physical object may have a given physical attribute, let's say color. Now, color is notoriously subjective. You might see green one way, I see it another, someone who's colorblind sees it as gray, a dog or a bee or a bird will all see it differently. The physical characteristics and events that make the object "green," however, are fixed and external to perception: it absorbs certain frequencies of the radiation we call visible light, and reflects the frequencies we classify as green. These are attributes of the object. When we perceive those attributes, we call it green; but green to me or gray to you, the object itself isn't different. The object and its attributes are in physical reality; your perceptions are your interpretation or understanding of that physical reality. That understanding is necessarily incomplete and imperfect, because your senses are limited and your brain is finite.
I think elevating different imperfect perceptions of reality to the status of independent realities of their own is the height of hubris. We don't create a new reality just by seeing the external one incompletely, any more than taking a photo of a fish in the lake creates a new rectangular lake that's mostly a fish. Read Plato's Allegory of the Cave. The shadows on the wall are perceptions of reality, but they're only shadows; they're not a separate reality in their own right.