There are some parts of the game that really might've been impractical on Wii, or at least would require very clever development staff.
And honestly, in this case Agent D's right. Half the appeal of Uncharted was how it pushed the PS3's Cell processor, and by going to 360 that might have been compromised, and if it went to Wii it absolutely would have. But this isn't really something that applies to Xenoblade, as I noted it probably would've been about as popular, at worst SLIGHTLY less so. It's the latest game from the Xeno team, and it's during a period where good JRPGs are scarce, just look at how rabid people got over Ni No Kuni, a game that probably would've been considered good but kind of bland during the late PS2 days. Failing that (because HOLY SHIT IT ACTUALLY HAS A WORLD MAP, something that's practically disappeared on PS2 onwards), then a similar game would've probably been considered dull on PS1. Certainly the DS game isn't much liked, and that actually gives a rough approximation of how it'd look on PS1, even if spells would work more like on PS3 probably. Though that does play very differently, so it's probably not the best example.