The Grand Theft Auto series was a very popular game series with many loyal fans. The question of which game was fun varied from person to person because everyone had different preferences for games. However, according to some game reviews and player votes, Grand Theft Auto 4(GTA 4) was generally the most popular game in the series. It had a huge open world where players could freely explore and carry out various criminal activities and missions while interacting and cooperating with other characters. The game also provided a high-quality action and driving experience, as well as a rich game story and character development. GTA 5 was also highly rated in many games. It had a more open and free game world, allowing players to freely explore and carry out various missions, while also adding more crime elements and social interactions. If you want to try the Grand Theft Auto series, I suggest you try Grand Theft Auto 4 first, and then you can decide if you want to try other games according to your preferences.