Never did Erector Sets. My problem with Tinker Toys and K'nex is that they seem limited to the "things built out of spokes and hubs" genre, whereas Legos (I say Legos, plural, so sue me) can do the spoke-and-hub thing but also tie that into the architectural realm--run a spoke through a block, anchor a gear to a block, etc. and you have mixed genres.
And I want to clear up a particular complaint that I do not have. I do not object to the "set that can only build one thing" because that complaint is, by definition, ignorant of what one properly does with Legos, i.e. store them in a big tub, possibly categorized, possibly pick-and-grab, and build from the imagination. Since the "picture on the box" may be built at most once, and likely never at all, it is irrelevant. I do recall the booklets suggesting plans for multiple items, and if this is no longer the case, then what is the harm done? Build something. Conversely, I can see the argument that the multiple plans laid out would constitute a "tutorial" in the use of new or unusual pieces.
To clarify, what I do object to is the rise of over-specialized pieces. That is, a piece molded exactly in the shape of something. This directly robs the Lego set of its potential as a tool of the imagination. And, why do we need this, when people have figured out how to build
Stephen Hawking out of stock parts?