*sighs* where do I start...
mate, I don't mean to be disrespectful at all, and I respect your opinion but I have got some thoughts to share.
I don't think developing games for the Xbox 360, or playing games on the platform, equates to lowered expectations. Eurogamer, IGN and Gamepsot do peridiocal comparisons b/w the same IPs on both platforms; Digital Foundry also goes through pain-staking HD comparison details; most of the time the Xbox 360 iteration is the better one, other times both platforms achieve parity, and only in select instances does the PS3 run away a clear "winner".
They say the PS3 is harder to develop games for and is hasn't quite been harnessed, so if that's your argument it'll make sense that MGS: Rising might be compromised to achieve parity on both platforms, but you aren't saying that now, are you? you are saying -- or at least you imply from your post -- that space, not programming dexterity [or the lack of it], is what makes a good game a good game. I don't agree.
For starters a lot of the space on the Blu-Ray disc [for MGS4] was for the cut-scenes, and you've gotta admit there were very, very many, very lenghty cut-scenes, some going well over the 30 minute mark
MGS4 had a movie : gameplay ratio of about 70:30, or more... as for Resistance, well I'm not quite sure why they needed 50GB for that game, I played it and loved it but nothing on there was stuff I hadn't experienced [or that couldn't be experienced] on DVD; Nothing on there necessarily required 50GB space [in my opinion], ditto Killzone 2, but of course a PS3 proponent will have 99 "facts" that he/she will use to prove me wrong
Personally, I think the argument that more space equates to better games has since become a quaint one: just look at Crysis on the PC or Gears of War 2 on the 360. I don't think the PS3 has anything as good-looking as either of those games, and I was a PS3 owner till very recently so have played very many of the biggest games on the platform...
I'm not here to tell you that one platform is better than the other, that'll just be pretentious, plus choice is good, and is necessary for gaming. It'll be a terrible indutsry if we had one hardware/software vendor and no one else... no, what I'm trying to say is that space, or the lack of it, on a chosen medium,does not mean a lack of depth in video-games.
Then again, what do I know