I don't see anything that won't fit on Vita's 960x544 screen. A DS Fallout game would require a new UI, true, but I don't see how it's a problem. Just because you have to split one screen into several doesn't mean you have to cut any attributes, skills and mechanics. As long as the PC version of the hypothetical game uses a different UI, everyone should be happy.
So the problem here is developers failing to create a custom UI for each version of the game they make. There was nothing preventing BioWare from using larger fonts in the Xbox version of Jade Empire, and there was nothing preventing Bethesda and Obsidian from redesigning the Pip-Boy interface in the PC version with PC displays in mind.
Publishers/money is stopping them.
Developers can't even finish their games and get rid of the bugs before shipping, they can't afford to add a whole new UI and some redesigns for the platform the sells the least. Just look around, some games like Skyrim are going beyond, completly ignoring the mouse and asking the PC player to plug-in a Xbox controller for "best experience"! They are clearly saying that they won't bother with the port, that PC gamers should "get on with the times" and "consolize" their PC! Can you see where all the hate comes from?
Besides, you are only looking a the changes in the surface, like the UI. Dialog and text has been reduced & dumbed down in games to work better on consoles. Just look at how the dialogs now are always short and even full-texted player replys can never exceed one or two lines.
Devil Survivor is great, but think of much the text was edited to fit the screen. Anwsers are shorter than on twitter, it's hard tell a good story this way. MCA's writing in PS:Torment would require you to scroll like 3 times just to see ONE of your 4 possible anwsers if ported to a DS. And we just can't ask MCA to be brief, can we?
Look at those descriptions, you know that we are never going to get anything like that again, unless on a PC-exclusive title. Things like party control, inventory, character screens, dialog, UI, combat logs, all are made with a different concept in mind when on handhelds or consoles. Those are core changes that not even the best port will change. The same way that consoles & handhelds can't manage RTS, there are some RPG elements that will never be done on them, like Baldur's Gate real-time-with-pause combat.
And that's the whole point of this debate, PC gamers know that they aren't getting the full potential of the RPGs, they know that if any of those games where done with the PC in mind they could have been better, more complete, even if just the writing, the controls or the graphics. That doesn't mean they are bad, just that
some people find the incomplete, inferior or simply put,
. Since you are on a PC gaming forum where most of the posters think that, (and also dislike JRPGs), it's easy to see why posters will just ignore handhelds as the "Heaven of RPGs".
I still enjoy playing them, but can't stop to think on how many good games and ideas have died because they aren't fit for consoles & portables.