I have searched any games that are similar to Project I.G.I., but the games recommended by so many netizens are almost always the same ones, such as: Medal of Honor series, Delta Force series, Tom Clancy's Splinter Cell series, Metal Gear Solid series, GoldenEye 007 series, Tom Clancy's Rainbow Six, Line of Sight: Vietnam, Thief series, Desert Combat series, Battlefield series, Operation Flashpoint, Hitman series, Crysis, Far Cry, Tom Clancy's Ghost Recon series, and more. But finally I found a game that is much closer (can be regarded as a remake) to I.G.I. series - Beyond Enemy Lines.