Pastor Nicholas T. Batzig makes the following remark in a sermon of his entitled, "Hard Pressed on Every Side": "Why are Gospel-preaching churches so small? Gospel-preaching churches are so small because the natural man hates the Gospel and will try to keep even his enemies from hearing the Gospel." The context of the statement is Acts 14, where we see the Gospel-antagonistic Jews shedding off their bigotry towards the Gentiles if only to prevent them from hearing and responding to the Gospel of the crucified Jesus. Such is the ignominy of the Gospel that other hatreds becomes loves if only to make it more hateful!
If such is the case, it may be asked to what message have these hordes of people who warm the seats of these ultra-mega-churches responded to, and by what means? Of course, mere numerical statistics don't mean error prima facie, but a mere cursory observation of the methods and doctrines (or lack thereof) of these churches would lend immense viability to Nick's statement.
For one thing, most of these churches subscribe to a paradigm of conversion that is best described as moralistic, therapeutic, deism. Preach on a subject that will foster discontent in the audience, though not about God's Law and sin—that's sure to cut the attendance by half the next Sunday! Let it be about relationships, how to carry on great marriages; or about the career, how to always be on top at the office. So you've been a failure as a husband or father; you've not been promoted in 3 years. Well, you need a Savior! Needless to say, the Gospel is not about eliminating the pet peeves from your life, but about what God has done, in Christ, to save you from Himself—with Christ living a perfectly righteous life (to satisfy God's demand of perfect obedience to the Law), dying on the cross (to satisfy God's demand of payment for your non-obedience to the Law), and rising up from the dead in order to secure for Himself a people imputed with His righteousness and declared justified by grace, through faith.
Secondly, they operate on a paradigm of conversion that is epochal. Given perhaps that the person and work of Christ was adequately preached from the pulpit (the Gospel), the working assumption is that this one time of having heard the message is enough to effect conversion, so then we have the proverbial "altar call" and "sinner's prayer." While the Lord is free to effect His saving work in such a case, it is more the exception than the rule. John Calvin states, "We are converted little by little to God, and by stages." Instead of the revival type of evangelism, it appears that the biblical mold is progressive indoctrination through Sunday preaching and Bible studies. The Holy Spirit uses the biblical truths of the Gospel as expounded in these venues, assimilated through the mind (noticia), to break its way through to the sin-hardened heart, making it realize (assensus) its need for a Savior (fiducia). This approach takes the radical depravity of the human heart and God's promise to bless His ordained means seriously. Dr. Darryl Hart gives a treatment of this in two blog posts: "The Unconverted Calvin: Part One and Two."
The Gospel's message and method are not the rave these days. No matter. Not a single one for whom Christ died shall be lost, even if his church is micro. ;-)