I don't know how to break this to you, but the Mopar V8 with the dome shaped combustion chambers isn't the be all, end all of V8s. GM's Gen IV motors are, well, better.
I'm not just saying this, either. I drove a 300C for a month while my GTO was in the bodyshop thanks to an inattentive driver in a Silverado. It was a nice car, but I didn't think the engine was quite up to the level of the LS2 I was used to. The biggest problem with the car was the 5 speed, however. It downshifted
very slowly, especially at highway speeds. It also makes it worse when you're used to choosing your own gears.
The car also has a very 'big' feel to it. Bigger than it actually is. I'm sure that the G8 seems better based on that alone, at least in terms of feel.
At the track, the 300 did better than I expected. Pretty good acceleration from a stop. I got 5.68 s 0-60 based on the built in timer, and my best ET was a 14.03 at 99. Makes me feel pretty good to beat the mag's time when the have 10 more hp.
Not on the level of a GTO, certainly, but very good for a family cruiser.
Based on my experience in those two cars, the results don't shock me. G8 being directly descended from the Commodore I'd expect it to be better than my GTO in most ways other than hp, and I think the GTO was better than the 300C overall.