Very interesting list. The Prime series has no shortage of memorable areas, and you did feature quite a few of them. Just thought I'd give my personal opinion on each of them.
Temple Grounds:
- I did like how the Federation ship was there, and how you got to scan through the entire horrific ordeal that they went through. Very catchy music, although I think we backtracked to this area a little too much. It was nice that it had so many paths to all the different areas, which made it a true over-world. Don't think I'd put it in my top 10 personally.
Bryyo Fire:
- The fuel jel atmosphere was something that was pretty unique, and kept it from being a clone of the Magmoor Caverns. The puzzle solving with the ice missiles was somewhat enjoyable as well, and the deep chorus as the music was okay. I would put Magmoor Caverns over it though.
Torvus Bog:
- Ahhh, I was hoping you'd put the Torvus Catacombs on the list somewhere, as it would probably place in the top 5 for me. Nothing ever really stood out to me about the Torvus Bog though, as I always think it's a chore to go through. The Catacombs were a much more memorable experience to me.
Skytown:
- I have to say, I loved this world. Metroid had never seen anything like it up until that point; we'd always had the water and fire levels, but not some kind of floating culture level. the Metroid testing facility really creeped me out, and stand as one of the more horror-esque moments of the series. It'd definitely be on my top 10 too.
Agon Wastes:
- Somewhat of a generic starting world, and probably my least favorite out of your list. I don't know, but I just never found too much in this world to be all that great. We get introduced to the dark world dynamic, but that's about it. It's actually one of my least favorite levels in the series.
Bryyo Cliffsides:
- I don't think it's nearly as good as the Bryyo Fire caves, but it still does have a unique atmosphere of its own. The abandoned culture and colossi made it stick out, and it did a good job of introducing how the Leviathans are screwing with the world.
Phendrana Drifts:
- YES. I loved this place when I first went through it in Prime, and I still do to this day. Like with Skytown, a snow level had never been done in a Metroid game before. Not only that, but Retro went the extra mile with the presentation and music. Truly one of the most beautiful areas in Metroid.
Tallon Overworld:
- One word: atmosphere. I think this area does it the best of any in the series. It truly feels like the beginning of the 3D Metroid era; gentle rain, main theme going on, waterfalls and grass... It's hard to explain, but this might be my favorite area of the entire series just because it FEELS so awesome. Excellent choice.
Sanctuary Fortress:
- Probably my favorite area in Echoes, just because, again, the series had never seen anything quite like it. A fully armed fortress, equipped with dangerous weapons and an awesome boss. It's pretty huge too, which really makes it worthy of "final level" title. It would be in my top 10 for sure as well.
Chozo Ruins:
- Hmm, can't say I agree with it being the number one spot, but I can see why you would think so. The Chozo were quite the enigma for us outside of Japan when the first Prime came out, and this world did an excellent job with the passive story-telling, and the tragedy that is the extinction of the Chozo. Worlds like "Great Poison" really put some tension in the story-line, something that Prime in general did an excellent job with.
Good video though! I personally would've put the likes of Torvus Catacombs, Magmoor Caverns, Pirate Homeworld, and Phaaze on mine, put your list was still pretty neat.