Silent_Buddha
Legend
You are ignoring installed (HDD) games as well as in-game transitions. I don't have a list handy, but many games in this gen use the HDD for swapping data, as an extension of RAM. Again, it especially affects sandbox RPGs like Oblivion and DA:O which suffer from terribly long in-game transitions.
In the long run, while playing a game, more memory means less need to reload data from either the disc or the HDD.
The effective 256M of main RAM isn't matching the rest of the HW in the 360 or the PS3.
Not really, more memory will ultimately mean either longer load times or more complex texture streaming. Even with an SSD on PC, loading up a game with 2 GB of textures (can't think of any game that does that except with 3rd party texture packs) would take a very significant amount of time.
And streaming only helps to some extent if you want really detailed textures.
As such I'd be very surprised if the next round of consoles have more than 2 GB of main memory and at most 1 GB of video memory with 512 MB the more likely sweet spot. 2 GB also makes it easier to port the game to PCs running a 32-bit variant of Windows (2 GB virtual address space per program). You can get access to more by making a program large address aware, but that is rare for a developer to do and 32 bit Windows is going to be limited to 3 GB virtual address space per program even with that.
Regards,
SB