Observations About Spiritual Gifts
All of the spiritual gifts are given out by the Holy Spirit and fit thusly into the general purpose of the ministry of the Holy Spirit, which is defined in Scripture as bringing glory to the Lord Jesus Christ (John 16:13-14). The gifts, then, are designed to direct attention, thanksgiving, and glory to Jesus and not to the one exercising the gift. Having and exercising a gift is neither a sign of spiritual accomplishment or maturity - but rather the undeserved and God-given enablement to better serve one another which causes all to recognize the presence of Jesus and stand in awe of His ministry to His Body.
In my own observation (i.e., a Mick-theory, not a clear biblical statement), I have concluded that there seems to be two types or classes of gift: (1) "Life-type" gifts, and (2) "For-the-moment" gifts. The "life type gift(s)" are given to each one when we are born again and will be regularly seen in the daily experience of the believer. The gifts listed in Rom. 12 seem to generally be of this type (perhaps with the exception of prophecy). A New Testament example of this would be the Cyprian Levite named Joseph (Acts 4:36). His life was so characterized by the gift of exhortation that they nicknamed him Barnabas - which means "Son of Encouragement".
The others, "for-the-moment gifts", are those which may be manifested on certain occasions to meet the particular need of the moment but then may or may not ever be again seen in that individuals life. In general, the list in 1 Cor. 12 seems to fit in this class of gift, although any of the gifts listed in the passage could most certainly be lift type gifts also. We are told twice to desire earnestly the gift of prophecy (1 Cor. 14:1; 14:39) and also to earnestly desire "the greater gifts" (1 Cor. 12:31). Some take that to mean to give emphasis to those gifts in the gathered congregation while others see it as an exhortation to ask God to impart certain gifts to us individually - especially prophecy and the "greater" ones. I personally lean toward the latter view.
What then are the "greater gifts" and why the stress on them and on prophecy? I believe the "greaters" (which are not specifically defined in Scripture) are the ones that most benefit the Body in meeting the specific need(s) it is experiencing at any given moment . It could really be any one of the gifts of the Spirit. The stress is also on prophecy because of the nature of that gift - it is a special communication from God somehow designed for the specific moment and ALWAYS edifies the Body (1 Cor. 14:4). Prophecy, then, would always fit into the category of a "greater gift."
SOME CONCLUDING THOUGHTS
Finally, let me stress the importance of walking in the Spirit and being available to be used by Him in any ministry situation in which you're found. Scripture never commands us to discover our own personal spiritual gift(s). We may not even know what they are and still be exercising some of them! On the other hand it is good to know what the gifts are and how they function so we'll be more expectant of the Holy Spirit's work in our midst since we have a glimpse of His "modus operandi".
Earnestly desire the manifestation of the gifts in your life - but don't strive or seek to manufacture them in the flesh. Surrender your life to the Lordship of Jesus and walk in the Spirit. Then enjoy what He does through you to touch the lives of others.