> I've never seen an Android that would get updates for more than 2 years (can anyone beat this with 3?)

That depends: Are you looking for updates to the new version or security updates?

Android One program gives you two years of regular updates, plus an additional year of security updates. My Nexus 5X received two major updates (from 6.0 to 8.0), but I kept using it until the security updates stopped. That's essentially three years of support.