So as a single-pokemon collector, I’ve been happy to see other people here doing the same or are very similarly-focused.
BUT!
For everyone else though, I’m curious.
If you HAD to collect cards depicting only ONE Pokemon. What would you choose? What card would inspire the collection? What would be your “Holy Grail”?
Groudon or Zapdos
To make it still very challenging: Pikachu 
Ive started collecting Raichu’s
Single pokemon collecting is a great fun for me. First off, it tends to be cheaper (if you pick a pokemon like whiscash) than going after rarer and rarer tcg items. Then it’s also a more focused collection i.e you always know what you want and no purchase is extraneous. Lastly it’s challenging, especially when you run out of the obvious choices for your poke of choice. This has allowed/forced me to learn about new merch/flats I would not have known about otherwise. There is SO much stuff out there for each pokemon it’s like a big ol’ treasure hunt
I have thought about doing something like that, but in the end I never did because of different reasons…
First, there is no Pokemon in the TCG which I like each and every artwork of. And I don’t see the point in collecting cards or things in general if they don’t appeal to me (not disrespecting anyone who does though). Also some Pokemon are highly under-represented in the TCG (e.g. Arcanine) and others are simply impossible to complete (e.g. Pikachu). And don’t get me started on some of the newer releases 
But to answer the question, the Pokemon which comes closest may be …surprise… Charizard.
Salamance or garchomp for me next
Gorebyss
I think its important to wash ones hands of the idea of “completing” a collection, because is it ever truly done?
Gyarados or Jolteon
Always zapdos
You beat me to it! Mewtwo would be my first choice. There are so many cards ranging in value and rarity. I think if I get that battle carnival card I will be set. 
Not when they’re pumping out new sets every few months!
Also mine would be Raichu
Ooh, this is a tough one. I think I’d go for either Rayquaza or Darkrai. For non-legends I’d collect Greninja, and pray that there’s going to be a secret-rare shiny Greninja card eventually. It’s pretty hard to choose when there are so many amazing cards on the horizon (Emerald Break, possible M Beedrill EX FA card) and possibilities for the future! (Sinnoh remakes, Gen 7, etc)
Actually, if you collect Kadabra cards, that might be the best shot at nearing completion. Who knows if it’ll ever be printed again.
I collect mainly Charizards but this upcoming set makes me want to collect Sharpedos… always liked using it in the games lol. If not, maybe Scyther, he’s pretty cool 
No love for Jynx? She’d be my choice.
I would have to say mew or celebi.
Tyranitar is one of my fav’s
Missigno, my collection is both complete and incomplete.
lol, but in reality: Mew.
Back in the day when Red/Blue were out Mew was a very rare thing.
Venusaur. A powerful cream puff:)