The G8 should have sold better than it has. It's a nice car and has a lot of Euro inspiration in its design, on top of that, the power/dollar ratio is killer, and right now you can get a G8 GT with under 10K miles for about $20K.... That is about the BEST bang for the buck out there.... and I'm not even talking about power only, I'm wrapping newness, Warranty, space, reliability, mileage, comfort, power, etc. into that factor.
Sure it's not the nicest car out there, but I was really impressed when I saw it, considering I've rarely, if ever found a GM sedan attractive. The car has a tight, relatively refined, and clean look to it. I think being a Pontiac hurt it a lot, as "Pontiac" has as much a cool factor to people nowadays as Oldsmobile did.
As for the Maxima, there is no way people identify the name with that old pictured example. The last two Maxima's have been nice cars, the most recent one being pretty damn stylish, definitely a more attractive car than a G8.