Quote: "Because oftentimes the concepts of game development are what you need to learn first."
True, although I think these necessary concepts depend on what you plan to specialise in, ie. programming, level design, and so forth.
Quote: "No, because Unity has excellent professional scripting capabilities. It's not very good for learning with. DBPro or AppGameKit, on the other hand..."
I think that's pretty accurate. Although for learning to program I would always recommend someone to start in C++/C# and work with console apps.
Quote: "What knowledge do you think is required to develop something like Unity? Definitely not the knowledge Unity teaches you. You may have a vague idea about how the underlying components work together, but all of the details are abstracted away."
It depends how much work you want to do yourself. Considering the huge community and countless tutorials floating around, I think it's very easy to get into using it and understanding all the different concepts.
Quote: "If all you know is Unity, then you will be forever dependent on people making game engines for you. Perhaps that's what you want, but it will only get you so far."
Well, who's going to make the next gen game engines? Not the average joe, that's for sure.
Quote: "Depends how you define "lesser". The Games Factory was a million times better as a learning tool for Young Me than Unity or Unreal could ever have been, yet the games you could create had only simplistic 2D graphics. Without it, however, I may never have gotten into the games industry and may never have even come across TGC."
That's true; for learning the principles it can be easier to use more simplistic software. I don't think Unity is unfit for purpose in this regard, but I think it requires a more mature mind.
Quote: "Although I love C#, I'm not sure it's quite an industry standard language yet. Everywhere I've worked in the game industry used C++ for most things still. C# might be on its way *because* of Unity, not the other way around."
Well, I assumed it's pretty standard outside of game production, but then I don't really have any experience in that area so maybe I'm wrong.