What is the Gospel?

Paul, to the elders in the church at Ephesus, in Acts 20:

And now, behold, I know that none of you among whom I have gone about proclaiming the kingdom will see my face again. �Therefore I testify to you this day that I am innocent of the blood of all of you, �for I did not shrink from declaring to you the whole counsel of God. (ESV)

Question: Is there a sense in which "declaring the whole counsel of God" is the same thing as teaching the gospel? (I would base this question on Paul saying that it is because he had declared the whole counsel of God to the Ephesians that he would be innocent of their blood.)

[For some of the context of this question, check out the many, many, many entries on the simple gospel at Adrian Warnock's UK Evangelical Blog. However, I think I'm asking a different question than Adrian: he's asking, "How simple can we make the gospel and still have it be complete enough to accurately represent the whole?"; I'm asking, "What's included in the whole? How complex is it, really?"]

[Update: There's more at Blogotional.]