1. Variety Of Tones
Perhaps one thing that has kept the series fresh is that the tone of the game is ever changing. From game to game and even mission to mission in the series, the series shifts between serious and ridiculous while never feeling disjointed. This is perhaps due to the criminal underworld aspect, where we often see it shifting from gleeful crime sprees to reality ridden sequences from scene to scenes. The series has jumped from the utterly neon landscapes of GTA: Vice City to the more reality sodden GTA IV and with almost ever itteration, the game looks at a different culture. This is something that I don't feel the GTA series gets enough credit for. No other major series has given us such a diverse and cultured set of characters and protagonists like this franchise. Whether it is the African American CJ, the Eastern European Niko Bellic, the Italian Americans in Tommy Vercetti and Toni Cipriani, even a chinesse protagonist in Huang Lee in GTA: China Town Wars, GTA has never settled on one culture for too long and it has kept things fresh and exciting.