Bottom line: To say GTA V has been a success is the definition of an understatement. In addition to generating more money than a small country's GDP, the game now has the distinction of remaining popular longer than an entire console generation.
The last entry in the Grand Theft Auto series first arrived on the PlayStation 3 and Xbox 360 way back in September 2013, just before the launch of the PS4 and Xbox One, both of which didn't see versions of the game until November 2014.
GTA V has remained incredibly popular throughout its lifetime---in 2018, the $6 billion+ it had generated made it the most profitable media product of all time, beating movies such as Star Wars and Gone with the Wind. With over 135 million units sold, it sits behind only Minecraft on the list of most popular games of all time, yet it continues to sell by the bucketload during Steam sales.
Earlier this year, GTA V became one of the freebies given away by the Epic Games Store, a move that attracted so many people it crashed the store.
As noted by Kotaku, Rockstar will be releasing an "expanded and enhanced" version of GTA V on the next-gen consoles in 2021, extending its commercial success into a third console generation.
While GTA V's main campaign is great fun, and players can enjoy the sandbox elements, messing around with mods, and so on, it's the game's online mode that's kept fans hooked for over seven years. GTA Online isn't without its problems, but the numbers of people it still attracts and the amount of money it makes in a highly competitive market speaks volumes. Sadly, that success ensures we wont's see GTA VI for a long time.