We need the gospels because we need the gospel. In the gospels we have the clearest picture of the incarnate Word who is himself good news for Adam’s race. And by memorizing and meditating on the gospels we can have a Christ-centered perspective on the rest of Scripture.
We are like the disciples on the road to Emmaus, foolish and slow of heart to believe all the prophets have spoken, slow to realize that all Scripture is really about Christ (Luke 22:13-35, esp. 22:27; also John 5:39-40). By starting with the gospels, we gain the perspective essential for profitably meditating on all other verses.
If we meditate on the gospels, Christ himself will put the rest of our memorization in its proper place and give us a Christian perspective on the Bible. He will warn us that eternal life is not in the Scriptures or in knowing the Scriptures (see Matthew 7, John 5:39-40) but in him alone (John 14:6, John 17:3). He will remind us that the Holy Spirit is the helper who teaches us all things and brings to our remembrance all that he has said (John 14:26).
I realized that I have a tendency to elevate the epistles over the gospels when I read a quote from J. I. Packer, which you can also read here. I need to know Christ better in the gospels, as well as the rest of Scripture. We need balance in our Bible reading, studying, and memorization; and we need a Christ-centered, Christian perspective on all of Scripture. May God open our eyes to see that the written Word centers on the grace and truth of Jesus Christ, who is the Word made flesh (John 1:14-17).
Do you have a portion of Scripture that you feel you need to spend more time memorizing and meditating on?