Why not Ecthelion?

[Galin]

Originally Posted by Yregwyn

Why was it Glorfindel that was reincarnated and sent back?

Tolkien seems to find a number of reasons why Glorfindel was reincarnated before the ban was lifted (which is different from being sent back of course, but being under the ban was problematic). He didn't list them like this, but here goes:

1) Glorfindel was an Elda of high and noble spirit (I'm going to assume exceptionally high and noble is meant)

2) he incurred the ban reluctantly only because of kinship and allegiance to Turgon, and love for his Kindred.

3) he took no part in the Kinslaying

4) 'More important': he had sacrificed his life, enabling Tuor and Idril to escape, a deed of vital importance to the designs of the Valar.

So Glorfindel was purged of any guilt -- in note 12 Tolkien describes that his guilt had been small, and once again refers to his noble character, among other things. He was released from Mandos, and Manwe restored him to bodily life -- and he gained the primitive innocence and grace of the Eldar. It is then said he became a friend and follower of Gandalf!

Glorfindel remained in the Blessed Realm, but his ultimate return (it is said) must have been for the purpose of strengthening Gil-galad and Elrond, in SA 1600 it appears.

Its just that Ecthelion killed what 4 Balrogs and then turned around and killed Gothmog. He dies as well but still thats 5 Balrogs, one being the greatest of them all.

It's already been noted, but these Balrogs were more destructible than Tolkien would later imagine them. I doubt these numbers were going to stand -- and actually, there is evidence that JRRT imagined as little as three, or at most seven Balrogs, ever existing.

The matter of Balrog numbers is a bit complicated, and involves 'when Tolkien wrote what' (as there are plenty of descriptions written when Tolkien imagined very many Balrogs existing), but the idea at least (in my opinion) notably calls into question the number of Balrogs that were going to be slain in any theoried, updated revision of The Fall of Gondolin...

... the detailed version of which never got very much beyond Tuor's coming to the city [see Unfinished Tales], although Tolkien did some updating with Maeglin too.