The most popular business class seats are Qatar Airways with their Qsuites, Delta Air Lines and their Delta One Suites, United Airlines and their new Polaris business class, British Airways and their new Club World Suites.
However, those seats haven't been installed on their entire fleet yet, so you risk getting the older business class cabin on a flight if you aren't aware on the operated routes.
Here's an overview of the present and future routes (with dates) of those popular business class seats:
Qatar Airways – Qsuites
British Airways – Club World Suite
Delta Air Lines – Delta One Suite
United Airlines – New Polaris business class