I don't know of any popularity poll. Who would be the best group of respondents to such a poll? Maybe past winners of the Nobel prize in physics?
Here is an interview on Bloggingheads with Frank Wilczek (a prominent theorist who shared the Nobel for quantum chromodynamics)
It has a six minute segment you can jump to that gives his view of string---"it's not really a theory" (in the usual sense of a bunch of equations and a mapping between the equations and reality).
This goes quite a ways towards answering the topical question--Why is String Theory Considered to be a Scientific Theory?
--that started the thread.
If you listen to Wilczek, a central mainstream figure in theoretical particle physics, then your basic conclusion is it is NOT considered to be a scientific theory
, by people who know what they are talking about.
That's all right---it's work in progress, an actual scientific theory in the conventional sense might eventually emerge. And there are branches of mathematics normally called "theory" that have no direct connection with the natural world: that are not scientific theories in the sense Inflector set out at the start of the thread.
My take on this is that it would help if people would try to speak precisely and acknowledge that it is NOT a scientific theory---that it is rather a body of mathematical theory with application in various areas but which has not, as yet, produced a theory of nature by accepted standards of Physics. I take Wilczek's word on this.