While the evidence for God is everywhere, there is no evidence whatsoever for ¨the devil¨ or demons or spacemen before the human mind abstracts these fantasies within itself. I believe scriptural references to these ¨beings¨ refer to God Himself as confusing as that may be to our species.
Read the book of I Enoch and you'll get quite a different picture. The link I provided is to the R.H. Charles interpretation of the Ethiopian Enoch discovered in the 1700's by James Bruce. It is interesting to note that I Enoch was also among the Dead Sea Scrolls and was thought to be highly regarded at the time of Christ and before.
To another issue (that of the existence of aliens), there is a significant body of personal accounts as to what is reported to be alien abduction (see John Mack, Harvard psychiatrist now deceased). While one may wonder what exactly is going on in these accounts, there is no doubt in the psychiatric community familiar with them that something is going on.
Also, there is plenty of information on exorcisms which while conducted by priests almost always include the participation of psychologists and psychiatrists.