What is the best cloud backup service?
The short answer
Backblaze is the best pure backup for one computer. It is truly unlimited at one fixed price and needs no configuration. IDrive is the best all-rounder for several devices under one plan. Acronis is the power option and combines image backup with security features.
In detail
A real backup service is different from a sync drive like Dropbox. It is there for the day your machine dies, gets stolen or gets encrypted. You then get everything back. Backblaze covers the essentials with great simplicity. You install it and forget about it. Every file on the computer and on connected external drives is backed up continuously, without limit and with version history. One subscription covers one computer. For a big restore, Backblaze can ship you a drive by mail.
IDrive suits households and freelancers with several machines. One plan covers your PCs and Macs as well as phones and even NAS devices. Versioning is strong. The Express service ships you a physical drive to seed the first backup. That helps a lot on a slow connection. Acronis is the enthusiast option. It creates full disk-image backups that restore Windows itself as well as your files. Anti-malware is included, and the price is higher to match.
Whichever you pick, the setup matters more than the brand. Include everything by default and keep versions for at least 30 days. Test a restore once to see that it all works.