GTA V was developed in four years. Star Citizen is now in development for… four years.
GTA V was in development from 2008 to 2014 (or 2015 if you count the Windows version). The SC crowdfunding started in October 2012. Rockstar created a game by improving on their own engine with an existing team and an existing gameplay as well as development formula. SC began with about 4 people and an engine not even remotely designed for their dream and got funded into pushing themselves further than initially planned and they now attempt to create a sandbox game unlike anything out there as well as a single player game at the same time as well as creating the team, methods and everything while doing it. I'm impressed with what they've accomplished with that in mind.