actually, no. DNA/RNA are in fact, just about the simplest chemical choices that can perform replication. Ribose, for example is the lowest energy pentafuranose, which means in a random mix of sugars you'll find ribose in the highest concentration. The funny thing is that the KSS principle seems to hold in nature, we've tried in the lab to design alternatives to DNA/RNA, and none of them seem to work quite so well.