Paul seems to indicate in 1 Corinthians 14:1 that the most important gift was that of "prophecy" - that is teaching. You could say that, yes, the ability to pass on the gifts is logically the "best gift" but that gift was restricted to the apostles only. See Acts 8:18. Since all the apostles died in the first century, that's when the gifts ceased. However, the word of God, or "prophecy" continues in His Word. So, for us at least, the gift of "Prophecy" would be the most important because we have the end result of that gift every time we pick up a Bible.