One of the great things about being a good guitarist, is that you can make simple melodies, repetitious songs, etc. much more intereesting. As a minimal guitarist, using the instrument just as backup to voice, I've tried to figure out ways to make simple songs less boring by using easy tricks like singing bits with no instrumentation, playing melody to emphasize certain phrases, especially if the melody can be found easily within the chord, changing tempo, delivering ballads with real feeling. Pick up a few simple bass runs but don't overuse them. Mostly, if you like what you're hearing, especially if you practice a lot, I suspect ;you're doing OK. Keeping oft repeated songs fresh is sometimes a challenge. Have fun...making music is a wonderful end in itself.