Duke Nukem Forever took about 14 years from 1997 to its release in 2011
The Last Guardian took 10 years, from 2006 to its release in 2016
Final Fantasy XV took about 10 years as well the original trailer was released in 2006 and finally released in 2016
There are also games that while finished development – never got an official release until decades later. The most recent may be Star Fox 2 – originally planned for release in 1996 – ended up getting released in 2017. That’s 21 years!