I've just reached the end of the
Lost Tales version and the first thing Christopher Tolkien says in his notes that the fact that Tolkien never revised Tuor's story right to the end (the Fall of Gondolin) is 'One of the saddest facts in the whole history of incompletion' and I really agree with him - it is! What a wonderful story it could have been if he'd taken it from Tuor arriving in Gondolin at the end of
Unfinished Tales and kept going with a full revision of Tuor and Gondolin's fall.
I cannot understand why he didn't

. It was one of the first stories he wrote (the first complete one, I think) and was dear to his heart - and yet he never came up with a final complete version of it. Tragic!
I think a lot of that story kept bubbling to the surface in LotR. Minas Tirith, as Riv says above, is a mini (though not quite so splendid) Gondolin. The Balrog makes a dramatic reappearance (they were a big part of the sack of the city), Glorfindel (where the reappearance of that name made him think about elvish reincarnation), and there is even a Legolas Greenleaf. It's all simmering there...
Those of you that have read the
Unfinished Tales first part of this story can tell me if there are any parallels in that while I get around to re-reading it

. It certainly seems to me that though he never properly finished this great story it kept bursting through!