Semantics. Just because I used the words "several years" you're gonna jump down my throat about it? Read, comment and move along.
It doesn't matter what development team finished the game, or what "version" saw the light of day, the actual DNF game was in development for 14 years. Plain and simple. It's not an argument. It's fact. You can't say that what Gearbox released was the only work on this game.
"On December 11, 2006, Sega announced they had purchased the electronic rights to the Alien franchise from 20th Century Fox. On December 15, Gearbox Software and Sega announced that they were working on a completely new game based on the franchise. In February 2008 the game's title was officially announced as Aliens: Colonial Marines; it was codenamed Pecan during development."