Is it possible that God appears to people in dreams these days? Can a person who spoke to Hashem in a dream consider this as a real dialog with God or should we instead consider it as pure work of our subconscious and imagination? Is there anything Chazal said about it?
Yas, many people see/imagine G-d in dreams in different forms. And Yes, people might think it is real, just as the Jurassic Park III movie.
Since the destruction of the first Temple, G-d does not prophecize people, so a dream of speaking to G-d is surely a hoax.