Many viruses from the herpes family are rather successful. Herpes simplex virus type-1 that cases cold sore stays dormant in human genome in over 60% of the world population. In some regions, that figure is 90% if I remember correctly.

And there's EBV too. "The Epstein–Barr Virus (EBV ) is truly prolific, with a prevalence of more than 90% in the adult human population." (source: https://onlinelibrary.wiley.com/doi/full/10.1111/apt.12503).