I would not presume to judge such a contest - those are all very good choices, and different people will have different favorites. I will mention one of my favorites, though, that I doubt would be mentioned by anyone but a horn player. It is near the end of the second of Strauss's Four Last Songs. Find the Schwarzkopf recording with the Philharmonia, Ackermann conducting, but most importantly in this case, Dennis Brain playing first horn. The most exquisite short little solo I have ever heard on recordings, and a favorite of a great many horn players. The original Angel blue label (at least I think it is without getting up out of my chair to make sure) LP sounds very good, at least the two copies I own both do. It is of course also available on CD, if one must, but that is NOT the same.
Almarg, that is most definitely a solo in the Ravel - the second horn does enter a couple of times, at first on the same pitch as the first horn, but then descending down a fifth from there, just the two notes. Most of the time it is the first horn alone, though. For me, Myron Bloom's performance of it on the Szell/Cleveland recording was perhaps the most beautiful of his recorded orchestral solos.
Cleeds, Adam is a great player. He mostly teaches now - full time major professor at the University of Michigan - but he was a member of the Philadelphia Orchestra horn section for ten or twelve years, I think, perhaps a little longer - he was the second horn player.