According to the web search results, the most popular Final Fantasy game is Final Fantasy VII, which was released in 1997 for the PlayStation and later ported to other platforms. This game has been praised for its gameplay, characters, and story, and has spawned many prequels, sequels, and spin-offs, such as Final Fantasy VII: Advent Children, Crisis Core: Final Fantasy VII, Dirge of Cerberus: Final Fantasy VII, Before Crisis: Final Fantasy VII, and Final Fantasy VII Remake. This game also has a connection to Final Fantasy X and X-2, as the character Shinra is a descendant of the Al Bhed inventor Shinra, and the concept of the Lifestream is similar to the Farplane.
However, popularity is not the only measure of quality, and different fans may have different preferences and opinions. Some other Final Fantasy games that have been highly rated by critics and players include Final Fantasy IV, Final Fantasy VI, Final Fantasy IX, Final Fantasy X, and Final Fantasy XIV. Each of these games has its own strengths and weaknesses, and offers a unique experience for the players. If you are interested in exploring the Final Fantasy series, you may want to check out some of these games and see for yourself what makes them so special.