Your saying that since the creators used valuable metals and gems as names for their games, and if they wanted to do the same for the 5th gen, the new gems/metals would have to be more valuable to top the previous names.
Yes and no. I'm not saying tops in terms of being a better name or anything like that. Any gems or metals used have less claim to fame. Their level of escalation ended in that realm though, yes.
It's like a roman numeral numbering system. I, II, III, IV. Eventually you need to shift over to something. You cant just keep doing I over and over. It's not IIII. So you do IV, you add something else to get yourself something new.
But since they already used the best gems/metals, that would prove extremely difficult. Does that about sum it up?
Unless you know of metals or gems with more notoriety and value, it's not difficult its near impossible. They've reached a plateau.
Now, I explain. That only holds true under two conditions:
1) The values of the metals/gems equate to the values of the names game-wise.
2) They wanted to top this gen, name-wise/game wise.
Of course both are false. The names are chosen based on how well they fit the games, not on how valuable the associated item is. And they chose Black and White for the same reason.
This is your opinion. I dont think any of the names really fit the games. I might associate lugia with silver, but, only cause they told me it does. I might think, white. So, why not call it pokemon white back then?
Even still, lugia is one part of that game and the silver wing a part as well. I dont see gold fitting gold really either. Really I think most of the games have little to do with their name. I mean, ruby just as well could have been called the land version, or magma version.
You think their names fit though, that's fine. Now I see where we differ. You see more in the names and the games than I do. You're able to see depth and make connections I have not made.
Here's what I think.
I believe they picked names ruby, gold, ect. because of what is associated with them. The value, the rarity, something that could be an heirloom or something you may never get again. These are things that you might associate with pokemon themselves. That could go along with fitting the game well. Really, why call ruby and sapphire those names? Why not crimson and indigo? Or something similar? Because they're not gem stones. I think they wanted something to peak people's interest a bit more than just color.
Black and white, dont hold that same value though. No one is selling black or white for 700 dollars an ounce.
It just makes sense to me, instead of doing more gems and metals, to change to something else entirely. They've done pretty much, the cream of the crop.
I dont think they arbitrarily toss names out there. I do think that the gems and metals were picked because of what's associated with them, and not just what color they are.