I’ve thought about this a lot in recent years and I’d like to hear your opinion on this topic.
Please restrict yourself to one reason that makes the Pokémon TCG the best collectible in your opinion.
I’ll start with mine:
The magical effect it had on young people…like my now adult sons AND continues to have on my 5yo daughter.
The community!
I agree with Gary. I personally had my first Pokémon memory from 7 years old (I’m closing 28 now). But because of Pokémon GO, the Detective Pikachu movie, and such, I’ve also seen young kids starting now. Pokémon spans loads of generations (Gary is a prime example of this as well 
).
In addition, there is so much options you have when collecting Pokémon TCG cards. Some examples:
There are so many different options on how to collect, and even if we all have different collection goals in mind, we all love collecting Pokémon TCG in general. 
I personally am very glad I returned collecting about 4 years ago, and I will continue to collect for a long while for sure. 
And hopefully I can one day make my kids and grandchildren be interested in Pokémon as well.
EDIT: And definitely agree with @poketrade as well. If there wasn’t such an amazing community here on Efour and some other places, collecting wouldn’t be as exciting as it is.
Greetz,
Quuador
It´s a combination of many things, number 1 reason for me personally is reach.
The fact that I can invest in something nostalgic that I genuinely enjoy.
I like the fact that the early sets are like a time machine; Every time you take a look at them, you’re transported back to that period in time where you enjoyed the cards with friends. And many people nowadays share that connection, which is awesome.
This.
I think people forget just how insane the craze was back in the late '90s. You couldn’t go anywhere without seeing Pokemon. Television commercials, online advertisements, billboards, etc. Every collectibles store was completely usurped by Pokemon (I still say the rise of Pokemon was the final death blow of Beanie Babies). It was unreal.
First we had the anime. Then Pokemon Red and Blue. Then the TCG. And it didn’t just stop there. There were endless Pokemon toys, whether they were those awesome Hasbro battle figures or those Pokeballs you could throw and they would automatically open.
It was the very definition of lightning in a bottle, and as popular as Pokemon still is and as amazing as its staying power is, nothing will ever match that initial boom. Not just in Pokemon, but in any other hobby in general.
That mania in late 1998 and 1999 was genuinely a once in a lifetime event, and I’m not sure we will ever see anything like it ever again. It gives me goosebumps just thinking about it, and it’s why I love this hobby so much. The memories never fade.
I don’t disagree with anything from the above already mentioned but I think things like nostalgia, community, etc are not things exclusive to the Pokemon TCG.
There’s one thing that I think really drives the Pokemon TCG and franchise as a whole that many other franchises just can’t replicate. It is the fact that:
Forget just the tcg, its the best franchise. What game did the world play more than pokemon go? That was the closest experience to the 90’s.
The numbers alone back up this claim; its the highest grossing media franchise! Pokemon hits every type of person, of every age. There is something everyone can appreciate, from casual to serious collector.
I wish I still had that screenshot of a reddit comment where someone who didn’t care about pokemon at all still had something like a pikachu pen, “jugglypoof” backpack, and some other stuff in their possession. Most people who don’t know pokemon will either know the phrase “gotta catch em all” or know the pokemon pikachu/mew or know the concept of Pokemon evolution. You really can’t say the same thing about anything related to MTG or Yugioh or DBZ or whatever else Pokemon is generally associated with. Pokemon did a really good job branding itself and making it a household name from the late 90s and onwards. They’ve also done well with staying relevant (whether its due to their own marketing i.e. Pokemon Go or due to pop culture i.e. Pikachu meme).
Pokémon by itself has become a culture. A culture in Japan and a culture for ‘90s kids’.
It is nostalgic in every way like an SNES and Donkey Kong Country or a piece of Magic the Gathering card you saw your brother’s friend showed off because you weren’t adult enough or even that specific issue of Sonic the Hedgehog comic you read when you were young.
Pokémon by it’s core is ‘gotta catch ‘em all’. The sole gameplay of the original Red/Blue was to help Professor oak complete the Pokédex. Beating the Kanto gym leaders and the Elite Four is just extra fluff to the ‘collecting’ game.
Culture, nostalgia and being a very collector-heavy concept, Pokemon is the best collectible out there.
Pokémon Red & Blue Gameboy Games & the OG Anime (with characters such as Bulbasaur, Charizard and cool gym leaders) made what Pokémon is today.
Without the nostalgia Pokémon wouldn’t be around today!
Today, Pokémon has to raise the level of the Pokémon brand to what it was in the 90s for it not to die out when the OG fans die out etc.
IMO Pokemon can do this by improving their video game quality, and improve the TV show to stand a chance of carrying on and not dying in the decades to come. They definitely need to partner with LEGO when their contact ends with the cruddy rival they went with.A LEGO contract will be huge for Pokémon.
TDLR; The Pokemon brand keeps the tgc alive and it’s why it’s the best collectable.
Definitely for the community. Its not as toxic and is a welcoming one when it comes to collectibles and affordability. We don’t judge individuals for their favorites or their goals and the old/newer generation will always have a nostalgia to their favorite Pokemon / characters / series and games.
I misread that as “universal religion”. I guess that’s right as well 
It’s the best cause it’s better than the rest.
Nostalgia.
There are some things you should know about Trading Card Games, and one of them is that there is absolutely no evidence to support the statement that Pokémon TCG is the best collectible out there. Pokémon TCG is 4th in complexity, 2nd in available variants, 3rd in number of artists, 3rd in amount of rarities, 5th in overuse of CGI and 3D, 3rd in art styles, 2nd in featured sets, 4th in original promos, and 4th in original character design. Pokémon TCG leads the world in only three categories: number of early child addiction, number of children who believe they can restrain wild animals, and cardboard spending, where they spend more than the next twenty-six trading card games combined, twenty-five of whom are direct competitors. None of this is the fault of a 6-year-old elementary student, but you, nonetheless, are without a doubt, a member of the WORST-period-GENERATION-period-EVER-period to “appreciate” trading card games, so when you ask what makes Pokémon TCG the best collectible out there, I don’t know what the fuck you’re talking about?! Baseball?!!!
Pokémon sure used to be.
Pokémon introduced us to nostalgia! Pokémon cards were fought over moral reasons, they passed and struck down other TCGs for entertainment reasons. Pokémon waged wars on collecting culture, not people’s creativity. Pokémon thrived, they cared about original art styles for rares, we put our money towards well designed cards, and they never cheated out. Pokémon built great big things, made ungodly product advances, explored the creative universe, cured boredom, and cultivated the world’s greatest artists and the world’s greatest economy on international products. Pokémon reached for the stars, and the company acted like people who appreciated the player base. They aspired to originality; they didn’t belittle it; it didn’t make them feel inferior. They didn’t identify themselves by who they placed for a quick dime, and they didn’t give up so easily on making quality work. And they were able to be all these things and do all these things because they were informed. By great men, men who were revered. The first step in solving any problem is recognizing there is one—Pokémon TCG is not the best collectible out there.
Theres enough variety that everyones collection can be different and unique.