The following document was prepared by Stefan Plantikow (Neo4j Cypher language designer).
It compares the three closely-related languages, PGQL, Cypher and G-CORE, which The GQL Manifesto proposes to be fused into a new standard GQL language, exploiting the very heavy overlap of their current and intended functionality.
There are clickable links to the specs/papers that describe the three languages within this document.
ytz-030r1-Summary Chart of Cypher, PGQL, GCore
This document was presented to ISO WG3 (international Database Languages committee that develops the SQL standard) and INCITS DM32.2 (U.S. standards body for the same area) at their joint meeting in Toronto, 15-18 May 2018.