posted on Dec, 21 2005 @ 02:47 PM
Well, I haven't played Half Life 2 but know quite a bit about the storyline.
One theory is that the G Man is actually Gordon Freeman from the future who has gone back in time to help himself.
Reasons-
Gordon Free
man they both include each others names.
Apparently their eyes are the same colour.
Also at the end of HL2, I think the G-Man says "We've been watching you Gordon, and people will pay for your services." or something along those
lines.
More info