How bad was "the fall of man"?

We all know that Adam and Eve ate the fruit of the tree and then sin entered the world.  But what exactly did they do?  What were the consequences?  Do we really understand just how bad it was?

Take a look at the temptations of Jesus in Matthew chapter 4, notably verses 8-10:

"Then the devil took him up to a very high mountain, and showed him all the kingdoms of the world in their magnificence,
and he said to him, “All these I shall give to you, if you will prostrate yourself and worship me.” At this, Jesus said to him, “Get away, Satan! It is written: ‘The Lord, your God, shall you worship and him alone shall you serve.’”

To paraphrase, Satan says "I'll give you all of the Kingdoms of the World if you worship me." What does Jesus say? "Worship God alone."  What is very notable at this point is what Jesus does not say.  He fails to respond with "Those aren't yours to give."  Sure, he could be cutting straight to the point.  But, lets think about this logically.  If we assign the "If P, then Q" structure, this would become:

"If (you worship me), then (you can have all of the kingdoms of the world)"

Now, Jesus said "heck no" to worshiping Satan.  But what did he not say?  In the "If P, the Q" form, if Q is impossible, the the entire point of the argument is moot.  Jesus did NOT say, "Pffft, the kingdoms of the world aren't yours to give, Satan."  Which he probably would/should have if it weren't true.  Moreover, Jesus does give arguments like this.  Remember when the Sadducees were asking Jesus about the woman who was married to 7 brothers (one after the other after each dies) in Matthew 22:23-33.  They ask, "Who's wife will she be in the resurrection?"  Jesus simply says, "There won't be any marriage in the resurrection."  That is, I don't need to explain, the question is irrelevant...

So, then, the kingdoms of the earth really ARE under the power of Satan.  I don't mean this in a "Satan rules every government" sort of way (though he certainly has some deep roots in ours).  I just mean that Satan must have real power on earth.  And Jesus acknowledges it.

Generally speaking, I don't like the "what does that tell you" kind of assumption arguments, but I think this is actually quite convincing.  Satan really does have power.  The only way he could have gotten it is from the fall.  Jesus gave Peter the "keys to the kingdom" and Adam & Eve analogously gave Satan the "keys to the earth".

For more information on this, you can refer to a book by Eduardo Siguenza titled "John Paul II, The Pope Who Understood Fatima."  I haven't read the book, but from what I have heard he explains this concept in much more detail.