Many in video game circles wonder, what or who is the G-Man? This article will be an extensive report on what the online community, and myself, believe the G-Man is or represents. The G-Man is one of the most iconic figures in the Half Life series besides Gordon Freeman. He, first appears in the Black Mesa labratory in New Mexico.
During this incident the G-Man guides Gordon Freeman (series protaganist) along the way to his adventure, and at certain times might appear, or even be watching the progress of Freeman. When Gordon defeats Nihilanth, the ruler of Xen, the G-Man teleports Freeman to safety and offers Gordon Freeman a choice. Freeman can either choose to side with the G-Man and accept a job, on behalf of the G-Man's employers or refuse. If he refuses, G-Man is thrown into an arena and consumed by alien creatures.
Half-Life 2 opens in a similar way with Freeman, awakening, it seems that in between Half-Life and Half-Life 2 Freeman was held in some kind of stasis in the G-Man's layer. And, then when the G-Man accepts a job on Earth, he releases Gordon Freeman who is the man who completes the G-Man's assignment.
Without going into too much details about the plot of Half-Life 2, the Earth is in a sorry state. After the events of Black Mesa, a portal opened from Xen to Earth and the Earth was overrun by creatures from another planet. The leaders of Earth consolidated their civilians into cities, and then the Combine (another alien empire, behind the events at Black Mesa) opened a portal that overtook all of Earth in the 7 Hour War.
20 years have passed and the Earth is under the solid control of the Combine. The G-Man awakens Gordon Freeman and sends him on a mission to destroy the Citadel tower. So, it seems that his business contract in the first game was to orchastrate the portals to Earth, on behalf of the Combine, and then in the second game he took another bid, to destroy the Combine's hold on Earth. In both cases he used Freeman, firstly to open the portal, and then to destroy it.
The G-Man is almost, certainly, an alien being who is of a mercanry nature. He sells his skills to various intergalatic factions, who for whatever reason have an eye on Earth and it's resources. Half-Life 2 depicts an Earth that is being heated up. There are dead forests, and lakes are drying up. Whatever wants Earth, wants it for the real-estate, and they want it dry. Combine Advisers in the game are sluggish creatures, worms.
Dr. Breen, the human overlord of Earth, who works for the Combine even states to Freeman that he had a choice of taking him out as a contract, but passed it up. Whoever, or whatever took the bid for Freeman wanted to eradicate and reverse the Combine's control over Earth.
It is in my opinion that the G-Man is an alien being who is a mercanary. He for whaterver reason has a great interest in Earth and has used his contracts twice on Earth, both involving Freeman. He works for his 'employers' who seem to be an inter-galatic alliance that may oppose the combine. And, for whatever reason Earth is critical to their plans at opposing the Combine.