How important an attraction in Christianity is the notion that God will return and prove Christians "right"?

The main attraction is becoming aware that God is real, that gracious love and forgiveness are available through Christ. The fact that one's eternity is secured does factor in of course, although one is more impacted by the realities of the now than such considerations. The presence of God, the Holy Spirit conviced one, and making one aware of God's love simulataneously is important. As for events probably far away, I don't know if they factor in much. The whole "end times drama" does entertain people though. Apparently the book of Revelation is a help in countries where there is a lot of persecution, as one can get a perspective on current miseries, as well as get reminded of God's Judgment on those who reject Christ and persecute believers.