Even if you don't believe that Jesus really is God, it seems to me that Paul still makes a pretty compelling argument for choosing good over evil. If you merely look at these two lists as a comparison of hedonism/anarchy on the flesh side and altruism/civility- I can't for the life of me figure out why anyone would deliberately choose the fruit of the flesh. Don't you see how those things will ultimately end up being self-destructive, not to mention hurtful to others and damaging to all you relationships?
God gave us His son, Jesus not only to set an example for us (demonstrate the character traits of the spirit-fruit), but as a sacrifice to atone for all of our fruit of the flesh. So that we could actually be capable of having a loving relationship with God the Father.
Once He had defeated death and the Devil, He sent us His Holy Spirit, who makes it possible for us to be more like Jesus- to have His same character traits. Why would we want this? You're kidding, right? Why WOULDN'T we?
I believe that God wants to make us more like Jesus so that we can have healthier, genuinely loving relationships with others. In part, that will pretty much just plainly make life work better, but when you think about it, it is all about love- which ultimately is what Jesus wants for us and coincidentally it will make us more approachable and appealing to others, thereby giving us opportunities to share Jesus with them.
Galatians 5: 13-26; Life by the Spirit
13 You, my brothers and sisters, were called to be free. But do not use your freedom to indulge the flesh; rather, serve one another humbly in love. 14 For the entire law is fulfilled in keeping this one command: “Love your neighbor as yourself.” 15 If you bite and devour each other, watch out or you will be destroyed by each other. 16 So I say, walk by the Spirit, and you will not gratify the desires of the flesh. 17 For the flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the flesh. They are in conflict with each other, so that you are not to do whatever you want. 18 But if you are led by the Spirit, you are not under the law.
19 The acts of the flesh are obvious: sexual immorality, impurity and debauchery; 20 idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions 21 and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God. 22 But the fruit of the Spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, 23gentleness and self-control. Against such things there is no law. 24 Those who belong to Christ Jesus have crucified the flesh with its passions and desires. 25 Since we live by the Spirit, let us keep in step with the Spirit.26 Let us not become conceited, provoking and envying each other.