GARN DAANUTH - the bad brother of Arion who last turned up (I think) in JSA Classified as one of Power Girl's visions just before Infinite Crisis. Can't see him turning up any time soon.
GEMWORLD - with DC taking a bit of a chance on a few different titles and genres with the relaunch, I suppose it's not entirely impossible that Gemworld might return at some point, but I don't think it'll be before the end of 2012.
GENTLEMAN GHOST - though I dropped Savage Hawkman after #4, I was aware that the Gentleman Ghost was due to appear in the second arc so he's going down as already in place.
GEO-FORCE - haven't heard much about Markovia's prince but it wouldn't surprise me if he were to turn up in the pages of Justice League International, if not as a hero then at least as Prince Brion but I'm not confident enough to call it.
THE GHOST - an old Captain Atom foe, I can't see this bloke arriving in the pages of that title, given the direction it's going in.
G.I. ROBOT - I'm putting this one down as already in place as a new G.I. Robot Squadron that looked like J.A.K.E. 2 appeared in the pages of Frankenstein Agent of S.H.A.D.E. and while it wasn't the same character, the essence was there.
GIZMO - the midget enemy of the Teen Titans. Yeah, we won't be seeing him.
weekly series featuring the Guardians, DC have (again, at least by mid-Feb) ignored the potential of the group who could be easily set up as antagonists to Justice League International. Will we see them by end of 2012? I doubt it, sadly. [Update - Dr Mist was name-checked in the DC Comics Free Comic Book Day The New 52 but didn't appear.]
GLORIOUS GODFREY - now that Darkseid's back in the pages of Justice League, there's always the possibility that his Apokoliptian cronies will reappear, though probably made-over and more up to date. I'm going to go with a possible here.
THE GOLDEN GLADIATOR - Unless the Gladiator manages to live for hundreds of years and turns up in the pages of Demon Knights, I can't imagine we'll be seeing him.
GOLDFACE - last I head, this old Green Lantern villain had sort of reformed and become a union boss in the Flash book. With GL's vulnerability to yellow gone the way of Hal Jordan's war crimes, I can't see any need for this bloke to return.
THE GORDANIANS - I think the Daemonites are the big alien threat for the DCU at the moment, so doubt we'll be seeing these old Omega Men bad guys.
So in summary, two in place (Gentleman Ghost and G.I. Robot), no definite predictions and one possible (Glorious Godfrey)