A few points.
1) Lumping Google in with Apple here is misleading for people who aren't paying attention to the industry more generally. Please note: Apple is way, way ahead of Google in this sector. People may find this confusing because Android is doing so well more generally (it's rapidly surpassing iPhone in phone marketshare), but that has not as of yet translated to significant game sales. It's probably worth including Android because eventually it could get better, but that's not where we are now.
2) I don't know if Sony or Nintendo has more to lose from Apple and Google's growth. Nintendo is the obvious choice, and people are largely focusing on them, because Nintendo has openly criticized the iOS model and because many of their blockbuster games last generation have clearly been consumed by iOS, such as Brain Training. On the other hand, Sony's entire purpose for being a games machine manufacturer is to create a trojan horse convergence device, which the PSP certainly tried to be. Furthermore, the PSP has ceded significantly more share over the last three years than the DS has, suggesting that empirically it may be the PSP-as-convergence-device that has been the hardest hit segment of the market thus far (PSP and DS lost similar market share last year, but PSP lost significantly more than DS the year before that). That could just be a coincidence (that is, it could be that the PSP was dying anyway), but it's worth noting as a possibility, and that empirically we've seen the PSP market falter much faster than the DS one.
Therefore, I see this as a very real and immediate but not existential threat to Nintendo, while it is a more remote, distant but truly existential threat to Sony. I'm not sure who to call the "biggest loser" there.
3) People are focusing on handhelds right now, and I agree that right now, that is the market under greatest assault. However, anyone who cannot project this just a few years in to the future and see it threatnening consoles isn't being imaginative here. I believe all portables -- that includes the 3DS and PSP2, not just the iPhone, iPad and Android -- are going to be threat to consoles in a few years. They already are in Japan.