I have to agree that the model was subtly modified to make it look better, but overall the model that was used for PS2 can't be upscaled. Instead, the model used for that picture which is in HD is vastly different from the old PS2 model, it's some kind of a "how it should have been if there were no hardware limitations" -model. There might be several problems for using that like missing animation and bending points necessary to create an in-game model out of it.
But yeah, I agree the eyebrows are a bit cartoony. The ears also have a difference as you noted, in which I prefer that HD variant of the old model (once again, that isn't used in the old games but only for promo art) better.
The reason Ratchet's face looks less furry except cheeks and jaw is that it lacks gradients in the middle part of the face. When there are no gradients, the furryness doesn't show up. That has been tried to be fixed for ACiT but as of now, the PS3 wouldn't be able to handle realistic fur like that in the PS2 promo model.
Don't you think this pretty much catches the furriness of the old model (tho the eyebrows are still a small issue)? Just like the one I posted earlier and that PS2 promo art model, it isn't the one used in-game, or at least PS3 doesn't use it on a resolution high enough for the characteristics of the fur to become completely visible (again right-click and choose "view image" for full size):
But I think we can agree that the exact model used in the PS2 games isn't the best one, but that HD one with the old characteristics you posted? It has neither the issue with the eyebrows, fur, enormous eyes, hands (seen in other promo art using the same model) nor out-of-proportion head.
Just keep in mind that it shares most of the characteristics with the 3D model used in-game, but it isn't the same, so the in-game model *can't* be upscaled to look like that.
Ratchet should also get that Megacorp helmet (or technically it isn't identical to the helmet in GC, but the same style) back. It fits well.
Finally, at least the eyebrows aren't as cartoony as they are in the Japanese games: