Zappo, I figured that I was going to get disagreement and people advocating freedom of religion and all that. And no derogatoritude is meant. Freedom of religion is good. It's very good. I like it a lot.
The short answer (since, um, I'm technically at work) is that I disagree with you. In part. I think that it IS possible to have complete faith in a religion you've invented yourself, even one that uses a philosophy you picked up from watching episodes of "Growing Pains" over and over again until blood was trickling out your ears. (I'm agreeing with you at this point.)
But (this is where I start disagreement -- not trying to be patronizing, just trying to keep the argument clean), worshipping something that was created specifically for entertainment or as a marketing ploy, in my opinion, does not pass muster. It shows a lack of ability to differentiate between the screen/page and the actual world. Without that ability, I don't think that faith is possible.
I'm sure someone will swing a dictionary definition of "faith" at me, but I'll stand by it nonetheless. Just as a creature who cannot differentiate between right and wrong cannot develop morality, a person who cannot differentiate between reality and entertainment cannot develop faith.
That's vague, I freely admit. And I'm sure there will be nitpicking, and what-ifs. What I'm saying is this:
There's a line.
I'm fallible. I don't know exactly where the line is.
Heck, maybe it's a strip and not a line -- maybe there are beliefs that work in certain situations for certain people. Some of my friends seem born to be Wiccans, while others would be directionless in life if they weren't Christian.
I can tell you that in my mind, Judaism, Christianity, Islam, and such are all on one side of the line, along with people who meditate and listen to spirit animals and believe that everything has a soul, including their car. The GOOD side of the line.
And I can say with complete confidence that praying sincerely to a god in a D&D pantheon that someone else created for entertainment purposes is firmly on the other side of that line in UnhealthyLand.
If the kid was saying, "Cuthbert's ideals are cool, I'm gonna try and live like that," I'd be fine. From what Stone Angel said, that ain't what the kid is saying. Ergo, me having a problem.
-Tacky
EDIT: Looked more carefully at your post, Zapster, and you did ask if anyone can define a valid religion. I will confidently tell you that I can in no way at all do that. I personally feel it depends on the person. There are Christians who are really really really unhealthy about it, and there are Wiccans who are really really really unhealthy about it, and it messes up their lives. Maybe messing up your life is not a disqualification for being a valid religion, or maybe it is. I don't know. I don't know how to separate the healthy Catholics from the unhealthy Catholics -- which is why I'm not trying.
But I CAN confidently say that the 16-year-old worshipping Cuthbert has some real-life issues he needs to deal with before stuff goes wrong. Stone Angel asked. That's my opinion, and only my opinion, with no weight whatsoever behind it other than a pretty religious childhood and a bunch of meditation.