In the past couple weeks at church, the pastor has inexplicably raised questions about the effectiveness of Paul's sermon on Mars Hill, noting that his time in Athens was apparently limited and that there were relatively few conversions noted. He attributed this to the absence in Paul's sermon of Jesus as the Messiah and his crucifixion.
Ignoring for the moment that it seems unlikely that we have the entire contents of Paul's sermon (I would think we have a summary of the main points instead), I have to ask by what criteria we're judging the sermon. These days we consider a sermon incomplete if it doesn't contain an altar call, even though this was virtually unknown prior to Charles Finney (whose exposition of theology seems a bit suspect to me). How are we to judge the effectiveness of any particular sermon, nonetheless Paul's?
He noted other features that seem strange: no letter to the Athenians is extant (by which I think he assumed that no church was planted at this time), there is no mention of Paul being driven from the city (as happened in Thessalonika, Berea, and Philippi), and no other special commentary is made concerning the church there.
To these points I would note that no letter is extant to the Bereans, despite the evident working of the Holy Spirit in that community. Neither was Paul driven from every single place he went to preach, notably Corinth. Regarding the church, it's clear that a church certainly did exist in Athens. Dionysius' name is mentioned as among the converts, and he is reportedly one of the first bishops of that church.
As to the initial arguments regarding the invocation of Christ's name and the crucifixion, we might note that the audience were primarily Gentiles, not Jews. The idea of a Messiah was known to the Jews, but by and large an alien thing to the Greek community. (Even if there were parallels, the expectations for the Messiah to the Jew were likely different than for the Greeks.)
It makes more sense to start with a natural theology, which is essentially what we see in Paul's sermon. God is introduced as the creator and sustainer of all life. The resurrection testifies to the necessity of judgment, and so the warning is sounded. (One wonders if Paul really didn't talk about the crucifixion when he talked about the resurrection of the dead. The resurrection pervaded his discussion with Jews, too.)
Far from being "ineffective," it seems more likely that Paul tailored the sermon to the audience. He preached the gospel full well (we can see correlations from Romans in what is recorded in Acts), and it had the intended result.
I confess I'm mystified by the motivation to cast doubt on the effectiveness of this sermon. I can only speculate, and I don't really want to do that without more information; but I can't explain why a discussion concerning the audience and the likely abbreviation of the sermon as recorded in Luke wasn't even mentioned.
