When was the last time you expressed your love for Jesus? When was the last time you, like the sinful woman in Luke 7, fell at his feet, washed his feet with your tears, wiped them with the hair of your.head, and covered them with your kisses? She had been forgiven much. That's why she loved much.
In John 21:15-17, Jesus asks Peter, "Do you love me?" Notice that he doesn't drag up the past. Nor does he ask about Peter's words and deeds. Instead, he asks about the attitude of Peter's heart. You can't fake love. We either love Jesus or we don't. The Ephesian church had lost their love for Christ despite their doctrinal orthodoxy (Rev. 2:1-7).
Love for Christ is primary because it's the attitude of those who've been forgiven. You can't have been forgiven by Jesus and not love him.
P.S. If we love Jesus, we will love his people too. This is another emphasis of our passage in John 21. Read my essay Sloppy Agape to see why.