Elementary

[The Man]

Never said it was a hard and fast rule.

You made a number of statements that suggested that it was very often the case. I think that is far from established.

Nope, never acted like this.

Really?

Really smart intelligent brilliant shows tend to have a much harder time finding a LARGE audience.

There are a rather substantial number of examples of smart, intelligent, brilliant shows that have found LARGE audiences. To the point where saying they "tend to have" a "much harder time" seems like a pretty strange statement to make.

Pretty sure I clearly said no one goes out LOOKING specifically for something mediocre.

You explicitly said it will find an audience BECAUSE it's mediocre - "it's just mediocre enough... that it will find it an audience". I am saying that it being mediocre (or not) has nothing to do with why it will find an audience. It will find an audience (or not) because it has (or doesn't have) qualities people like. Those qualities have little to nothing to do with "mediocrity".

I think there is a difference in semantics. I don't see mediocre shows as 'bad'. More like ordinary, average, nothing special.

One of the definitions of "mediocre" in my dictionary and at dictionary.com is "not satisfactory, poor, inferior". This squares with how I've generally seen it used - if people meant to say something was "average" they would use "average" or "nothing special" or something like that. "Mediocre" has a much more negative connotation than "average".

May be a regional usage issue, though.

To put it another way, if there were a seven-point scale these would roughly correspond to the rankings:

Terrible - Bad - Mediocre - Average - Good - Excellent - Classic

Sherlock on the other hand is very extraordinary and special. Americans seem to not like quirky or special things unless they are marketed and presented in a very specific way.

Sherlock is certainly extraordinary but I don't think it's really any quirkier than any of the other adaptations of the Holmes canon I've seen. It's a bit more British than some of them; that's about the only thing I can see that makes it potentially offputting to American audiences. Most of my friends love it, although admitted my friends are probably not a representative cross-section of American television audiences, but the reception has been extremely positive consistently enough that I'm fairly certain that if it were the subject of a more extensive marketing campaign it would be able to find a much larger audience. As I've said, I think the main reason Elementary got so much larger ratings is because it was marketed much more thoroughly.

The "standard crime show with a Sherlock Holmes twist" summation is a fair argument - that is a legitimate reason that people would want to watch it. That is not what I was seeing above.