To achieve carbon neutrality, it is necessary for city gas companies to develop low-carbon transition strategies to reduce the greenhouse gas emissions and to prevent their assets from becoming stranded assets, since natural gas is a type of fossil fuel. This paper designed a quantitative method to evaluate the low-carbon transition strategies of the three largest city gas companies in Japan and the five largest city gas companies in China. This paper also evaluated hydrogen and e-methane strategies by the “S + 3E” principle. The conclusions are as follows. (1) Major Japanese city gas companies have more robust low-carbon transition strategies and therefore rank higher than major Chinese companies. Chinese city gas companies should raise their ambitions to include the Scope 3 emissions reduction into their strategies to achieve net-zero. (2) Major Japanese city gas companies have more comprehensive hydrogen strategies than their Chinese counterparts. But Japan faces more challenges to develop hydrogen than China, in terms of energy security and economic efficiency. (3) Japan is a promotor of e-methane and one of the leaders in e-methane technologies, but the challenge to develop e-methane is still huge, especially from the perspective of economic efficiency. (4) Both Chinese city gas companies and Japanese city gas companies begin to transition into integrated energy companies by developing renewable projects, but Chinese companies have an edge in deploying renewables. (5) Major Chinese city gas companies place a higher priority on methane emissions control than their Japanese counterparts in the low-carbon transition strategies. It is stressed that the opportunities for cooperation between China and Japan are huge in hydrogen and e-methane, and a “Technology × Market” linkage promotion mechanism is proposed.