Some options: 

Nestea in korea and thus probably best in the world...

I've been really impressed with Sheth.

He is the anti-Idra.  Nicest guy in the world.  Makes it easy to route for him.

I've become quite a Losira fan these past few months.  And I like watching July due to his relentless aggression.  Idra becomes a beast as the game goes on, but people are right about his whole mental block problem.

But best?  Hmm... I guess Nestea has had some kick ass games.  I dunno.

Sheth's ZvP is monstrous and Idra's ZvT and ZvZ is also really nice.

Zergling number 700457 won the Zerg olympics last year, so I guess I would have to go with him.

ZvZ probably Nestea, ZvP or ZvT probably July

"

"

July, for being the most badass in game, and IRL.

1. Losira
2. Dimaga
3. Nestea
4. Idra
5. July
6. Sen
7. Ret
8. Fruitdealer
9. Sheth
10. Morrow
11. TheWind
12. Catz
13. Zenio 

Things to note:
I included Losira because i think it would be a huge mistake not to, but other then that I only used the zergs you listed.
I have not really seen many Mondragoon games, definitely not enough to feel comfortable ranking him in this list.
While TheWind, Catz, and Zenio are 11, 12, and 13 respectively, I would not include any of them in the top 25 (maybe not even top 50 =/) of the world (again i only used what you listed + Losira)
TheWind definitely shows top 10 in the world potential, but sadly is a coach and doesn't practice a lot because of that, which makes me really sad =(

"I feel comfortable saying MC is the best Protoss but can't name a best Zerg or Terran. "

When it comes to watching streams I like Steven Bonnell II (ROOTDestiny). He certainly isnt the best in the world but I like how he has a different personality.

From what I've seen (which includes zero GSL games), I really like Idra and Spanishiwa.

i would say Idra in a ZvT or ZvZ. For ZvP, I can't think of someone. 

i really want to see more of Min from SlayerS

Losira and July are my current favorites

Nestea easy

Destiny is my favorite.

CatZ.  He may not be the best technically, but he has tons of fun playing, which is the most important thing.  I steal his builds because they're awesome and insanely creative and I've learned a ton on how to play zerg from his stream.  You can't be mad when you lose to his cheeses because they are simply too hilarious and clever.  My personal favourite is the proxy hatch to block a Protoss from walling off then running in with lings and killing him.

Here's me doing it on my Random account.  It's a build he used to do on Steppes of War but recently found it works really well close positions Metalopolis, Slag Pits, and Shattered Temple, all spawns that are incredibly hard for Zerg to play macro games in anyway.  I've only lost once doing it because I went proxy hatch to proxy hatch instead of cancelling and making my expo.  The way to beat this build is to make 2-3 cannons, but then you can cancel the hatch and expand, which made the Protoss waste tons of money getting a forge and cannons while you lost about 80 minerals from the cancel so it is best to place your cannons such that you can cancel if the Zerg cancels.  I played pretty bad this game because I was too busy laughing.  Even when it fails I chuckle because of the ridiculousness.  So far I'm 2 for 2 on getting BMed at the end of the game.

http://www.sc2replayed.com/replays/165136-1v1-protoss-zerg-metalopolis   

For Korean Zergs, I've been a Losira fan ever since he came back into the tournament.  He always looks so happy.

@Positrark said: 

" ZvZ probably Nestea, ZvP or ZvT probably July "

You sure Nestea ZvZ? I'm pretty sure Idra has a 90% win rate in ZvZ...

"

" CatZ.  He may not be the best technically, but he has tons of fun playing, which is the most important thing.  I steal his builds because they're awesome and insanely creative and I've learned a ton on how to play zerg from his stream.  You can't be mad when you lose to his cheeses because they are simply too hilarious and clever.  My personal favourite is the proxy hatch to block a Protoss from walling off then running in with lings and killing him.

Here's me doing it on my Random account.  It's a build he used to do on Steppes of War but recently found it works really well close positions Metalopolis, Slag Pits, and Shattered Temple, all spawns that are incredibly hard for Zerg to play macro games in anyway.  I've only lost once doing it because I went proxy hatch to proxy hatch instead of cancelling and making my expo.  The way to beat this build is to make 2-3 cannons, but then you can cancel the hatch and expand, which made the Protoss waste tons of money getting a forge and cannons while you lost about 80 minerals from the cancel so it is best to place your cannons such that you can cancel if the Zerg cancels.  I played pretty bad this game because I was too busy laughing.  Even when it fails I chuckle because of the ridiculousness.  So far I'm 2 for 2 on getting BMed at the end of the game.

http://www.sc2replayed.com/replays/165136-1v1-protoss-zerg-metalopolis    For Korean Zergs, I've been a Losira fan ever since he came back into the tournament.  He always looks so happy. "

Sadly, Creativity doesn't have much to do with skill.  I think everyone here would agree hands down that CatZ is the most creative zerg. "

I'd personally go with NesTea... the guy is a total beast, he picked appart Jinro without any real problem, Jinro being a player IdrA lost too in 2 GSL Ro16(?) and then in the show match that annouced the NSAL

I think it has to be between Nestea and Dimaga. I hope to see more of Dimaga in future GSL's so I can say for sure which is better. July, Losira, and Idra round out my top five.

" I'd personally go with NesTea... the guy is a total beast, he picked appart Jinro without any real problem, Jinro being a player IdrA lost too in 2 GSL Ro16(?) and then in the show match that annouced the NSAL "

Idra is really really talented. He currently has a 78% win rate, playing a zerg which is pretty wild (Terrans tend to be the most stable players generally). He also has a really great understanding of the game, which I appreciate.

Idra said Losira is basically an even more macro focused version of him.  Losira will soon be like Nestea mk.II if he keeps improving.

" Idra said Losira is basically an even more macro focused version of him.  Losira will soon be like Nestea mk.II if he keeps improving. "

" @Ben_H said:

" Idra said Losira is basically an even more macro focused version of him.  Losira will soon be like Nestea mk.II if he keeps improving. "

 Nestea said Losira was the kind of player who you'd show one thing, and he'd learn 10 new things. He's growing really quickly. Hopefully he makes it far in this GSL! "