Hmmm, I think several different issues are mixed up here, so in order to clear this up (at least as I see it) let me just remind you that there is a difference between the reality as you see it and the actual reality. The reality as we see it is based solely on our own senses and brain. Our brain processes all external input (like sight, hearing, chemical input like smell and taste, etc) to create an interpretation of reality. This is the only reality we are capable of sensing / seeing, so yeah - this reality only exists because we exist. However, if you're referring to the actual reality - yes, it existed long before us and will keep existing long after...

Thing is, like Sageous said, the dream reality can't be compared to the actual reality. Not only that it was never real in the first place, it's not even based on real-time input (like the reality as you see it), but instead based on our memories, emotions, and expectations. Now, yes, dream reality can get pretty complex and convincingly "real", but this is only compared to the reality as you see it. Since both of these are generated by our brain (based on real-time or recorded data), it's not that surprising that both can have a similar level of realism. After all, certain drugs or medical condition that cause hallucinations can incorporate ideas we normally associate with dreams (e.g. unicorns) into "reality as you see it".

However, the actual reality is far more complex and beyond our sensory comprehension. As such it can't be, by definition, compared with reality as you see it or dream reality because it is not based on our own human senses. Furthermore, no matter how complex of a system of sensors we are going to build, we will never be able to fully comprehend the actual reality. This can be proven! First of all, based on the uncertainty principle (which has been proven) there is a limit to the precision at which we can observe or measure things. Furthermore, to comprehend a system fully you'll have to use sensors that are bigger than it or run thru the system for longer than it exists (if the sensor is too small to scan all at once) - but obviously we can't build a sensor that is bigger than the universe or one that will run for longer... Finally, it's mathematically proven that a finite set of axioms can't yield a model that is both complete and consistent (aka Godel's incompleteness). All three arguments essentially say the same thing, albeit from three different perspectives (physics, engineering or math), that you can't fully comprehend a system that you're a part of.

So essentially what I'm trying to say is that it's important to distinguish between our individual version of reality (or the collective version of it as a species - which is fairly consistent because we all have fairly similar senses and brains), and the actual one true reality. Now I don't care how big is that one true reality, if the multiverse exists it's still all located in that one reality. This one reality does in fact exist, so our presence as observers plays no role on its shape / existence. However, realities that are created by our brains or by a set of computer sensors are realities whose existence is relative and dependent upon the existence of the observer / measurement apparatus that conjured them.

I'll steal Sageous' punchline - tl;dr:
1. Actual reality - exists and is not dependent on observers to exist.
2. The world as each of us sees it / the world as the collective human race sees it - all of these worlds are a creation of one or more brain + sensors and are thus relative and their existence is dependent on the observer. However, they are as close to realism as we can get, as they are based on real-time input (unless certain drugs or medical conditions are involved).
3. A dream - like (2), it's relative and observer dependent, but instead of being based on real-time input it is based on our brain's creativity and past experiences, which makes it far less "real" than (2).

My two cents...