So many posts but only one or two dealt with the question I raised in the OP. Most posters seemed only interested in listing some IMO relatively minor additional set of etudes they were familiar with. Oh well.
Ah, I missed that you wanted an actual ranking.
MacDowell Ètudes Op. 46 - Reason: While some of these [IMHO underrated AND concert-worthy] ètudes indeed focus on the normal topics such as virtuosity and dexterity (examples: Moto perpetuo, Elfentanz); others are focused either solely on sonority (examples: Improvisation, Traumerei), or have a mixture of virtuosity and sonority (example: Wild Chase).
Liszt Transcendental Ètudes S. 139 - Reason: In addition to a heightened sense of virtuosity (examples: Mazeppa), some of these ètudes foreshadow other great composers. Liszt was really a genius at predicting trends of impressionism, and even atonality (although the latter is not shown in these ètudes). Harmonies du Soir and Chasse-neige predicts Debussy in more ways than one. Feux Follets was a favorite of Busoni.
Chopin Études Op. 10 & Op. 25 - Reason: These are great ètudes for poetic content. Very few of these ètudes are made to show off (the only real examples of showing off are in Op. 10 No. 1 & Op. 25 No. 11). The rest are made as ètudes for the heart (examples: Op. 10 No. 3 & Op. 25 No. 7), not the fingers. Which is kind of ironic, considering ètudes should be for the fingers (although they should be musical!).
Henselt Ètudes Op. 2 - Reason: While they're not of the highest originality, these ètudes can help you learn how to stretch your hands naturally (example: Op. 2 No. 11), without the kind of machinery that broke Schumann's hands! These ètudes certainly have their value (example: Op. 2 No. 6 [which Rachmaninoff liked]), and musically they may be out of place next to Chopin or Liszt, but technically they are there. Busoni liked the Op. 2 No. 1 well enough to include it in his Klavierübung.
Moszkowski Ètudes Op. 72 - Reason: Let's keep the reason short and sweet, because these ètudes are indeed short and sweet. It can act like the bridge between Czerny and Chopin, in poetic content (example: Op. 72 No. 14) and in technical challenges (example: Op. 72 No. 11). Vladimir Horowitz, when he was alive, saw great value in the Moszkowski ètudes and often played No. 6 in F, which has since been hackneyed to death.
Scriabin Ètudes Op. 8 - Reason: Yes, No. 12 is hackneyed to death. But does anyone really look at the other Scriabin ètudes' musical content? (Example: Op. 8 No. 4 in B major) is truly poetic, in a way that only Scriabin could be. They hint at the mystical qualities that Scriabin would discover in himself later. (Example: Op. 8 No. 5 in E major) has some of the big stretches that you found in the Henselt.
Saint-Saëns Ètudes Op. 52 - Reason: Well, for starters, Op. 52 No. 4 "Ètude on Polyrhythms" is a great way to learn polyrhythms, and indeed, it's how I learnt polyrhythms in the first place. Op. 52 No. 6 "Ètude in the form of a Waltz" however, is truly a concert piece. Gyorgy Cziffra used to love playing the "Ètude in the form of a Waltz", and when you hear it, you'll understand why! It's a great encore!
Saint-Saëns Ètudes Op. 135 for the left hand - Reason: Well, they're for the left hand. These ètudes for the left hand are more baroque (neo-baroque?) in nature, but they conquer some of the challenges a pianist who doesn't have such a good left hand NEED to face in order to improve their left hand. (Example: Op. 135 No. 3 "Moto perpetuo")
Alkan Ètude Op. 35 No. 5 "Allegro barbaro" - Reason: The full set of Alkan Op. 35 ètudes may be somewhat musically interesting, but only one ètude in this set of twelve in major keys, really makes you want to "rock and roll" in a way only Alkan could. That's the 5th ètude - "Allegro barbaro". It's an octave study in F Lydian, and it's just as chaotic as Bartòk's piece on the same subject.
Czerny Ètudes Op. 740 - Reason: Yes, they're very abstract and unattractive. But they make for great encore pieces if you take the time to play it musically. (Example: Op. 740 No. 3) It also doesn't purport itself to be music of the highest order, so one could argue in favor of making your own endings to the ètudes! (Raymond Lewenthal certainly did.)
I missed a lot of ètudes that I also wanted to rank, so excuse me.