It may be helpful to actually think about how vividly you remember you experiences of every day moments. It has been said many time by many wise people that as much as we would like to think otherwise, much of humanity spends nearly all of their hours believing they are truly awake when the reality is that they are far more passive, more reactive, and only think that they are thinking. Many times only those memories that are most meaningful, odd or emotionally charged are given sufficient lasting power and detail to remain vivid and "real". Plus, we deal with the real all the time, so all too often does the detail and awe-inducing nature of reality seem dull and diminished because we are simply exposed to and filtering it all the time.

Likewise, the very nature of dreaming can very often grab your attention because not only is the context strange and unfamiliar, otherworldly even, but the very processes of consciousness are working within a different context. Some areas in your brain are functioning at a higher level, some at a lower, so in some ways the mechanism for perception, for memory, is in itself novel.

Another thing to keep in mind, though I'm not positive how relevant it is, is that dreams are merely (or more obviously) a construction of your mind whereas waking reality is at least slightly more fixed. In a dream your brain is providing all the stimulation and response, while awake the external environment provides the stimuli and all your brain has to do is try and make sense of it. Perhaps the more intimate connection to the root of the experience, the fact that you are subconsciously creating your surroundings, the dream characters, events and actions make it easier to have a deeply connected and more vivid experience of the dream.