#135 Calvinism is the Gospel

What is the gospel? What is missing from the modern watered-down version of the gospel? Was C.H. Spurgeon right when he said that 'Calvinism is the gospel'? What did he mean by such a statement?
From the sermon 'A Defence of Calvinism':
"There is no soul living who holds more firmly to the doctrines of grace than I do, and if any man asks me whether I am ashamed to be called a Calvinist, I answer—I wish to be called nothing but a Christian; but if you ask me, do I hold the doctrinal views which were held by John Calvin, I reply, I do in the main hold them, and rejoice to avow it."
–C.H. Spurgeon
"The old truth that Calvin preached, that Augustine preached, that Paul preached, is the truth that I must preach to-day, or else be false to my conscience and my God. I cannot shape the truth; I know of no such thing as paring off the rough edges of a doctrine. John Knox's gospel is my gospel. That which thundered through Scotland must thunder through England again."
–C. H. Spurgeon