Towards the end Pontiac had alot of rebadged cars but in the G8s defense... Can you get a Holden here? No. Could you import a Holden here? Sure, if you have money falling out of your ass I suppose. Would you be able to drive it in the US? Probably not, IIRC they won't pass US EPA standards. Whats the closest GM car availible in the US similar to the Holden? The G8 is it if your in America. Thats the plain and simple truth. No other GM line has anything close to date. I'll own a G8 GT one of these days, make a nice family IMO and its LS powered too. Thats beside the point though.
As for GPs, Montes, and Impala being copies, that can be argued... When the Monte Carlo came out in 1995 (IIRC) is took the same frame and driveline from the Pre-Gen GPs which were around since 1988. Then later came the Impala. 1996 the Riviera got the L67 series 2 which the Grand Prixs and Regals got the option in 1997. Impala and Montes didn't get the L67 until 2004 when the next Gen Grand Prix was out. Hell the Montes used the 3.4 DOHC from the 1996 GTPs until 1998 when they finally got the L36 in 1999. See what im saying? Sounds like little kids pointing fingers at each other.
We can **** around here all day arguing who copied who, but it all seems to stem from the pre gen GPs which were out first. But who cares? Anyone care? Doubt it. I think 1997-2003 GPs are unique in there own ways and i wouldn't classify them like the G5 and the other **** out there. Not because i'm a GP owner, because of the history lession above. Same goes for even the 2004-2008 GPs too.