(DISCLAIMER: If Japanese were included, I'd put X and Y's "V Volt" as #2 on this list because it's seriously amazing.)

For my first ranking, I decided to cover something not normally discussed, which is ranking which opening for the english Pokemon TV series is best and worst. I'd like to start by saying that numbers 21 through 13 I see as legitimately bad, while 12 begins the streak of ok openings, and after 5 I say they're all phenomonal. Feel free to rage if my selection disappoints you. It's perfectly logical to start an argument over which opening to a kids show is better. (SARCASM.)

(Only some listings will have a video if I feel like it's necessary. This list goes from worst to best at the end. That should be obvious, but you never know.)

#21 (The Absolute Worst In My Opinion.)
"Under The Alolan Moon" (OP #21)
From Pokémon the Series: Sun & Moon: Ultra Adventures

https://youtu.be/FAjFlsebXaA

UGHHHHHHHH! I hate the Sun and Moon Anime, but this opening just makes me want to never watch the dub again. At least most Pokémon Openings weren't exactly pandering into any demographic, but clearly, there was an executive that thought this is what the kids like. The insufferable programmed drums ticking in the back along with horribly autotuned vocals create a sound I loathe, and the lyrics are also cringey.

We've been preparing, sharing, training.
Studying from A to Z.

What exactly are you preparing for the for? I thought this anime was supposed to be a sliceoflife with a laidback comedic atmosphere. This thing sounds like there's a big battel afoot, when there isn't. Also, there' s a huge lack of studying done in this show. The sharing line makes it sound like Care Bears.

'Cause it's coming soon.

What exactly is coming soon? I know the anime has this whole ultra guardians arc, but aren't they going after ultra beasts. I didn't know that ultra beasts or something else was threatening them. MY GOODNESS THIS IS BAD! Just name all the Pokémon next time or something... This is way worse than 4Kids raps. (That was longer than usual.

#20
"Under The Alolan Sun" (OP #20)
From Pokémon the Series: Sun & Moon

Sun and Moon did not have a good streak with me. I saw the Japanese opening and thought it was fine, but this just lacks any fun atmosphere it originally had. The vocals and the instrumentation is way more watered down from X and Y, and it sounds like you could make it on Garage Band on an iPhone. Also, the "money shot" where Pikachu is running and the legendary Pokemon are running with him and then Mimikyu shows up, yeah that shot, is given one small cut during the shortened English opening, which ruins how well-animated it was and takes away the best part of the original opening.

#19 
"Rival Destinies" (OP #15)
From Pokémon Black & White: Rival Destinies

This is the most harmless and utterly boring opening that Pokémon's ever had. Plus, it's lazy. The vocals and instrumentation are just really bland and uninteresting. The worst part about this is how the visuals look. They didn't animate a new opening like they usually do, and instead, they just cut and pasted a bunch of moments from the season and put them together as some average AMV. It's really just boring.

#18 
"We Will Be Heroes" (OP #11)
From Pokémon Diamond & Pearl: Battle Dimension

The first Pokémon OP with female vocals. I don't hate that part. It's just that this is another boring opening that's not nearly as catchy as the other Pokémon themes. My least favorite part is how this is one of the first times they really push the "we will be heroes and change the world if we try" motive, which bothers me because of this.

Ash was never intended to be some superhero saving the world, he wants to be the best, and I liked the original motive of becoming a Pokémon Master, not saving the world like every other Shoenn protagonist gets roped into.

#17 
"Battle Frontier" (OP #9)
From Pokémon: Battle Frontier

This is more petty than anything for me. I used to like it, but now it just sounds kind of annoying after repeated listens because of how sing-songy it gets.

#16
"Be a Hero" (OP #18)
From Pokémon the Series XY: Kalos Quest

Once again, the hero agenda strikes. Everything else in this opening is average and harmless, but that one line at the end...

The future of the world is in your hands.

No, it isn't. This isn't the season with the world-saving arc anyway. This line is just a cheap way to sound like they tried.

#15
"Battle Cry (Stand Up!)" (OP #12)
From Pokémon Diamond & Pearl: Galactic Battles

This one is more OK than We Will Be Heroes because the whole Team Galactic arc was about saving the world. Plus, the lyrics are ambiguous about being a hero and more about rising up against adversity, which is much more pleasing to kids, I guess. It's also more catchy than We Will Be Heroes, but still tiring after repeated listens.

#14 
"It's Always You and Me" (OP #16)
From Pokémon Black & White: Adventures in Unova

This one has better visuals, solid vocals (the "Oh, Ohhhs" are surprisingly poppy for Pokémon), and I guess the lyrics are fine. Nothing too interesting, but the synth line during the entire thing is slightly interesting when listening with headphones because you can hear it clearly.

#13
"Diamond and Pearl" (OP #10)
From Pokémon: Diamond and Pearl

It's a rap. 

Then again, it's pretty catchy for a rap, and it's the last really ear-wormy opening until Kalos. Kudos for that.

#12
"Pokémon Theme (Version XY)" (OP #17)
From Pokémon the Series: XY

While it's a little lazy to just bring back an old classic, it's still pretty catchy, and the full version is even more fun. They keep the stellar 3D camera actions shots from V Volt (the way better Japanese OP) while still shortening it. This begins the much better openings on this list.

#11
"This Dream" (OP #7)
From Pokémon: Advanced Challenge

I always thought this one started really abruptly, and the only catchy part is the part where they shout "This Dream last forever." Overall, still a fun opening. 

#10
"Pokémon World" (OP #2)
From Pokémon: Adventures in the Orange Islands

This one is bursting with funk. It's only at the ten slot because I forgot it existed, but once I remembered, it's fun.

#9
"Stand Tall" (OP #19)
From Pokémon the Series: XYZ

Talk about epic. Finally, we've returned to the idea of Ash being on a quest to be the best.

I stand tall cause I know that I'm a winner.

That line is a great one to hype someone for any Pokémon battle. It's also pretty catchy, but a little too short in my opinion.

#8
"I Wanna Be a Hero" (OP #6)
From Pokémon: Advanced

I know I ranted about the hero thing, but this is the least annoying version of the hero part. Because it sounds more like Ash just wanting to prove how epic he can be. Plus, the first part to this song is frickin' amazing.

#7
"Born to be a Winner" (OP #4)
From Pokémon: Johto League Champions

The way this opens with the lyrics of the original theme song with a cooler sounding delivery is awesome. The "Johto" chants are cool, and the visuals somehow remain cool and in tact after cutting off a minute of original content.

#6
"Pokémon Johto" (OP #3)
From Pokémon: The Johto Journeys

Come on, this song just makes you smile if you're a Pokémon fan. It's goodhearted, encouraging, and kinda makes you want to grab your Pokewalker or Pokémon Go and venture out into a rose-colored world. Also, the feeling of vastness is really captured with this song during the scenes where Pokémon are running alongside our companions. It makes the Pokémon world feel vast and full of life through song and visuals. The best part is, in the end, they always remind you that the end goal and purpose of Pokemon is still to "catch them all and be the best that you can be." 

#5
"Black and White" (OP #14)
From Pokémon: Black & White

https://youtu.be/ieKb00z1z7E

Visually, this is the most creative and aesthetic opening that Pokémon has. It's entirely CG, and the animation for it is captivating and stylistic, especially because only the Pokémon are in color and everything else is, well, Black and White. The message here is not exactly "deep", but it's a lot more thought-provoking than normal. Finally, we have a message that isn't about either friendship or being a master/hero. The song itself takes some time to get used to, but eventually, it'll get stuck in your head.

#4
"Believe in Me" (OP #5)
From Pokémon: Master Quest

This one is just flat out epic, and is purely about being the best, and I love it to death. This is more inspiring than any cat poster ever will be simply because of how catchy it sounds. Like, Pokémon openings back in the day were more annoying than the jingles from commercials. This one was also a key favorite of mine back in the days of being a 7 year old.

#3
"We Will Carry On!" (OP #13)
From Pokémon Diamond & Pearl: Sinnoh League Victors

https://youtu.be/rLDMsDtKrWc

Yes, this is cheesy, and yes it's slower, but this is how you open up one of your biggest seasons for your show. Sinnoh got a whole season devoted to its Pokémon League, and what better way to present it than with the pounding of drums in a stadium. The visuals are reserved for building up the fight between Ash and Paul along with the rest of the leauge, and the last visual at the end of and Ash and his team facing the four trainer's he'll battle during the league is exciting and makes you anxious to see it.

#2
"Unbeatable" (OP #8)
From Pokémon: Advanced Battle

Another minute long opening! Lord Helix, thank you!

This is personally the most catchy in my opinion, even over my number one pick, and I think that the visuals are stunning for Pokémon standards because they're not chopped up for time constraints. Chanting "I'm Unbeatable" makes me feel invincible, and I personally find this song uplifting. Also, Team Rocket gets my favorite shot of them when they're digging the tunnel. The guitars sound really nostalgic and laid back until they explode into an epic whine at the end of the chorus.

#1
"Pokémon Theme" (OP #1)
From Pokémon: Indigo League

No surprise here. It's too iconic. This thing went platinum because it sold so well. While many Pokémon fans can't remember all the openings, every fan can sing this one by heart. It's not the most catchy to me, but it is the most nostalgic, and the same can be said for almost every Pokémon fan. This song came from an anime that introduced many people to Pokémon, and a bunch of other anime as well. It's held in a special place in a ton of people's hearts, and judging by the fact that Pokémon has had two remakes within the last five years, it's here to stick around. Lot's of people hate 4Kids, but they deserve credit for creating what most consider to be the best opening to a kids show ever.

Whelp. If you just read the numbers and not the explanations, I'm perfectly fine with that, because I rambled a lot about some of these. Thanks for reading. Please vote, comment, and follow me for more. Tell me your top five in the comments if you want.