Discussion - Should Rainbow Dash Be The Leader? · 1:13am Dec 2nd, 2015
The finale got me thinking. IMHO, other than Twilight, Rainbow has always been the second-most important cast member. She's the one that's got an ongoing storyline with the Wonderbolts, along with Rarity and to a lesser extent Fluttershy, she's had some of the most significant character development of the six, she's the one of them most famous after Twi herself, and her human counterpart is given higher prominence than the other four.
However, the finale showed us Rainbow's importance to Equestria goes beyond her value on a meta-level. If she never did that Sonic Rainboom, the destiny of Equestria would be radically altered. The fate of the world hinges on Rainbow Dash. Not Twilight, Rainbow. She plays a role in Equestria's fate that can only be compared to Twilight's.
That aside, think about Twi's role in the story. In the first episode, she has this mysterious "spark" that brings the Elements back, a dubious plot device, true. However, beyond that, Twi is a bystander up until the confrontation with Nightmare Moon. She doesn't actually bring any of the group together, she was ordered to meet four of them by Celestia to check up on preparations, and Pinkie threw a party for her because she does that for everypony new to the town. Literally any other unicorn could have been sent to Ponyville in Twi's place, and would have met the other members of the Mane Six just the same.
Beyond that, Twi's importance in world-changing events stems from her magical prowess, or sheer coincidence of the plot. She's the one who frees the others from Discord, because she's the only one who can...except Celestia didn't intervene and surely could have. She's the only one to see through Chrysalis' deception, but because she's the only one who knew Cadance as a kid, if it was anypony else Shining Armor was marrying Twi might not have been so perceptive. She flat failed to save the Crystal Heart, we all remember it was Spike who saved the day (twice). Her battle with Tirek was based solely on her being an alicorn and for some reason Tirek not knowing she exists so she gets to be powered up, but by the same logic he shouldn't know Cadance exists and she could have taken on the power of the other three, too. Otherwise the day is saved by all six characters and their keys; Twi just happened to be the last one to get hers.
The only thing Twi has going for her as main character material is that it is apparently her destiny to become the Princess of Friendship, as indicated by the Tree of Harmony bearing her cutie mark on it and her cutie mark being the Element of Magic itself. However, unless one presumes some other sequence of events happened without the Rainboom that still resulted in Twilicorn, Twilight's destiny is dependant on the destiny of another: without Rainbow Dash, Twilight never would have become Celestia's student.
And, if only for aesthetics - one could easily argue that Rainbow Dash's six-hued mane is symbolically fitting for the heroines and the Elements of Harmony, more than Twilight's abstract "one large star with five others circling it."
If nothing else, Rainbow is certainly the deuteragonist to Twilight's protagonist. What about you guys? Think maybe Dashie has a horn coming in her future? 
YES. ALL THE YES.
I have this image of Nightmare!Dash, CrystalWar!Dash, and Harmony!Dash all ending up in a three way battle... and Harmony!Dash manages to get them to work together. Because SHENANIGANS.
I can agree with everything said here
wow, you just might be onto something here, though if the writers ascend one of the other five, their probably gonna ascend all of them. OH! someone's gotta write a story about this idea! i know id read it
No. Dash is important, but she isn't exactly leader material. If Twilight doesn't get to lead just for bearing Magic, Dash shouldn't get to just for performing a single deed whose significance wouldn't become clear for years. Let's face it, Dash is lazy and self-obsessed, has poor prioritization skills, and is utterly ruled by her emotions.
If we're talking leader figures among the Mane Six, literally any other member would be a better choice. Fluttershy rules the Ponyville fiefdom of the animal kingdom, Applejack and Rarity run businesses, Pinkie plans centuries in advance, and it's not like Twilight's gotten anypony killed.
Of course, that's not really what you're asking, is it? Character prominence and who should be in a position of power are two very different questions. It's true that Applejack and Pinkie Pie don't have the clearly delineated character arcs of Rarity and Dash's quests for excellence in their fields, Fluttershy's emotional growth, or Twilight's grand destiny. However, this is less a matter of being less important than it is having already largely found their place and being happy with it, and even then, they still have ways to grow beyond what they were.
All of the Mane Six have their moments in the spotlight and out of it. Dash just stands out because... well, she's Rainbow Dash. That's what she does.
Rainbow has strong significance, yes. Destiny altering significance even. But she isn't really leader material. Like
3586042 said, she's a lazy narcissist with the ego of a small planet. She set the wheel in motion and is critical to the fate of Equestria, but she's no leader. In my head, Applejack is always second-in-command if Twilight isn't around.
3586042
3586256 Applejack has common sense, which is rarer than platinum in ponies. I'd definitely trust her to be the leader more than anyone else.
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3586042
Now i'm imagining a Wolverine and the X-Men type plot where Twilight goes missing and Rainbow has to grow into a leadership role while the group seeks a new bearer for Magic to face some upcoming threat.