There are other tasks related to game interaction such as physics simulations too.

https://www.youtube.com/watch?v=O04ErnJ8USY (Destuctible environment.)

https://www.youtube.com/watch?v=LhcgjPFykXY (Fluid dynamics.) 

And are those parallelized  or serialized?

Obviously parallelized LOL. Those effects can ONLY hope to ever run on a CPU and if you looked at the first video on top you will see it running on a GTX 680. 

Don't you mean GPU? I thought those were for parallelized tasks while CPUs did things in series?

You need to be a little more sharper than that.

Isn't a GTX 680 a GPU though? If so, then clearly it can't "only hope to ever run on a CPU".

It's just me belittling CPUs in general and how truly weak they compared to GPUs.

After it can "ONLY HOPE" to ever pull these things off.

I don't think we will see many developers "coding to the metal".
It was a rarity on the Playstation 3 and Xbox 360, so with that in mind one has to assume the status quo would continue on with this next generation.

Most games use 3rd party game engines and 3rd party middleware then adapt it all to the low-level and/or high-level API's and call it a day.
For example, Mass Effect, Batman, Bioshock, Borderlands and Gears of War all use the Unreal engine that interfaces with the low or high level API.
Oblivion and Skyrim use Gamebryo or a variation there-of with various middleware like Speedtree in Oblivion. (Oblivion used a High-level API on the consoles, hence why it ran and looked like crap, but ran like silk on a PC vastly slower than the Xbox 360.)
Don't forget the plethora of EA games all pushing Frostbite and the CryEngine, Unity Engine and Source Engine powered games either who aren't done to-the-metal. (Probably many more in that list!)

The obvious cases were "coding to the metal" had it's advantages were with the first-party developers who then built their own game engines or heavily customised an old one such as was the case with Halo 4. (Albeit, used allot of Pre-baked lighting and shadowing and removed the tessellated water and had simpler geometric architecture in order to drive up everything else.)
Such games really had nothing else come near it in terms of image quality even after a year of being on the market.

However, the PS4 would be easier to code to the metal in comparison to the PS3, lots of 3rd party open-source tools, documentation and skilled developers who have been working with x86 and AMD/ATI GPU's for decades, that's going to pay off in spades, not just for the Playstation but for the Xbox and PC too.

It is compared to a high end PC, not ps360. ps3 had a 550mhz clocked GPU, ps4 is clocked at +-853mhz

PS4's CPU runs at around 1.6Ghz, just half of the PS3 and 360's 3.2GHz CPUs.