Antivirus Testing and Certification By Independent Test Labs
Many websites claim to know the "best" antivirus but this can be many factors including value, support, ease-of-use and of course if the website if being paid to feature that antivirus software. But, if you are looking for an antivirus product which scores the best in real-world anti-malware detection tests than you need to follow the independent test labs.
These independent labs usually test quarterly on same day malware threats and score each antivirus software on detection and usually give out awards to providers who detect 99% of threats. This is an ever changing landscape and each results with each lab can give different results this is why it's very tricky to pin point any antivirus as being truley the best.
There is also a regulatory body which sets the standards for the testing labs called AMTSO (Anti-Malware Testing Standards Organization)