There are a handful of modern pro wrestling championships that perhaps eclipse those on this list, but lack the historical significance on which too many coast. The PROGRESS World Championship in latter years has become known as a golden ticket to wrestling stardom. Similarly, the ICW World Championship acts as an inroad to prominence in the current wrestling world, with an overseas defence compelling the promotion to rename it from the ICW National Heavyweight Championship in 2015. This formalisation was unnecessary. When, for example, WWE announced the creation of the Universal Championship in 2016, it met no such criteria. It was received as a World Championship before it was even defended in the U.S.. It is received as a World Championship when it's barely defended now. That's WWE for you, hence the inclusion here of a certain blue makeweight.
It's also wrestling, plain and simple; whether or not a title is worthy of the World designation is a pure work.
CMLL, AAA and even the Americanised Lucha Underground are not included here, partly because your writer admits almost total in-depth ignorance of the lucha libre scene, but also because, in the case of the former league - by some distance the most enduring, popular and prestigious of the three - the 'World' designation is distributed across several weight divisions.
Ultimately, it's a subjective feeling; which championships project themselves as championships as a result of history, scale, reach and longevity of promotion, protection, perception on the international stage...?