Thomas Shey
Legend
Very little. There were a few things of the mass of Dragon content that became official content, but even looking at the early years of the magazine, it wasn't a big percentage.
We tend to remember the big things that DID become part of the game, but overall most of the content in The Dragon didn't make it in.
Cheers,
Merric
On the other hand, if you go all the way back to the short run of The Strategic Review, quite a bit did.