Alright, so the Ness boards convinced me to come out here, and normally I'm not too comfortable with doing this.
Anyways, I want to first mention that using Techei's videos from S@X streams is NOT a good measurement of the matchup. Techei is good yes, and no offense to players like Coreo and Shuriblur, but they aren't even PR material for our region. If you want a fair measurement, you should consider matches between the highest level players for the characters in the region. That would be me, Mik! and Techei. Normally, Techei beats these okay Ness players on stream, but whenever Techei and I play, I usually get the better of him. Similarly, you can't base your matchup input on mediocre Ness players you come across in tournament yourself.
Now for my own personal matchup analysis. Reading through this, I can pretty much agree to the fact that Ness off stage with PKT2 is pretty much dead. If the Greninja is paying attention, or not reeling from being knocked away, he can almost guarantee a HP gimp. However, Greninja really has no way of setting this up consistently. Ness being off stage is NOT a 50:50 on the DJ read. If you just look at the options he has, he can DJ+air dodge, DJ+aerial, and DJ into an instant PKT right under the stage lip. No, you cannot react and HP that last one, I'm talking about instant PKT ledge snapping here which is actually quite safe.With Ness' very fast aerials with good range and priority, and Ness won't be forced out of his DJ very often unless the Greninja player got a very VERY good read.
When it comes to just edgeguarding in general, I feel that neither character can do much to each other. Greninja just doesn't have the coverage and meaty hitboxes to pressure Ness out of his DJ and setup the gimp. His fair isn't even as close to being as bad as Sheik's. It's much slower and easily avoided. As for Ness, a smart Ness will never DJ for an edgeguard lest he get his stock turned on him. He should always save that DJ for getting back. Add to that the fact that Greninja has shadow sneak which is really hard to punish unless used aggressively, and he won't be getting much more than one aerial on Greninja either.
And let me state right now that none of us Ness players even care about the Greninja nerfs. The difference between Greninja players thinking it's a good matchup because of gimping being a "cop out" and Ness players saying nerfs as a cop out is that no Ness players even brought up the nerfs. Heck, I didn't even play Techei until after the nerfs were already done. Like seriously, Luco, Noa, nor I have ever even mentioned Greninja nerfs anywhere. We don't think Ness wins because of the nerfs, we think Ness wins because he's got the tools to handle Greninja. The nerfs just happen to be there, and they don't change much about the matchup at all.
On the ground, yes Greninja beats Ness, but so do a lot of other characters. But I'm still firm on believing that he only beats him by a little bit. Realistically, both characters are usually just trying to set up grabs. Ness for his combos, and Greninja for his uthrow. Greninja has setups into his uthrow on the ground and Ness does not, but Ness can set those up with his aerial, particularly uair. The the shuriken isn't really bad at all, more of just a nuisance. They don't even compare to needles. Ness can actually nair right through them (the small ones at least, the big ones are an easy bat reflect and shouldn't be used often in this matchup). But a small advantage on the ground just isn't enough to make a NEss matchup bad for him. If that were the case, Ness would be low tier, since most characters beat him on the ground. You need a SIGNIFICANT advantage on the ground here since the moves that Ness DOES land on the ground usually yield high damage or knockback (PKF and bthrow).
I can't believe the argument was made in this thread that Ness' KO options aren't that good. Really? Especially in comparison to Greninja, Ness is a GOD at killing. I'm convinced that Ness has the best KO options in the entire game. They're fast, low risk, pretty generous with their hitboxes, and pretty strong. At least, the good ones are. There's really no arguing it here, Ness doesn't even have to set up his kills like character such as Fox and Greninja himself. No uthrow in KO, no dash attack into KO, no jab cancel into KO, just raw bair, uair, and bthrow do the trick. And lemme tell you, having a good KO grab option instantly puts you in high tier on the KO potential list. I'm sorry, but Greninja's usmash or uthrow to uair just can't compare. When it comes to KOing, Greninja just has to put so much more on the line, all while Ness is throwing out bairs constantly with little to no risk.
And did I really hear that Ness uair has a small hitbox? That thing is a nair in disguise lol. I've hit people below me with that thing.
Now for the aerial game. I think most players can agree that Ness wins here. But what some people fail to see is just how well Ness handles Greninjas aerials himself. Not only are Ness aerials way faster than Greninjas, but they just outpriotize and trade so well with them too. Greninja's fair just gets beaten to the punch so easily despite its range. When it comes to bair and uair, nair just beats them so easily. It hits Greninja right out of it, and even if it trades, its a very positive trade for Ness. And Greninja can't afford to be trading aerials with Ness all game considering how much better Ness is at killing than Greninja. Greninja's common kill setups often involve uthrows into uairs, or usmash reads. Ness breaks out of that uthrow setup so easily since his air dodge and nair are so good. Nair just stops the uair if they trade. I mostly get KO'd by usmash reads.
When it comes to damage and combos, I feel it's a very slow aspect for each character. Both of them are capable of mitigating each others damage fairly well. Greninja can shadow sneak out of dthrow fair combos (Techei does this to me all the time, it's annoying), while Ness breaks out of Greninja's throw sets with his small stature, air dodge, floaty jump, and combo breaking nair. But I will mention that if a Ness player is smart with handling the shadow sneak combo escapes, he can catch the Greninja player on the end lag. Ness can also just for for the dthrow uair combo for a solid amount of damage that can't be escaped. I still feel like Ness outdamages Greninja in this matchup. Don't underestimate how much Ness can do if he gets in on you.
Honestly, I feel like I'm detecting some downplay on Ness' KO and damage potential coming from the posts in this thread. Ness is like Ganondorf's son in this game lol. Don't sleep on the hurt he can dish out in a short amount of time.
I've played Techei a lot at this point, so I feel like I have a good handle on this matchup. Like I said, I more often get the better of him, and if I were to put a number on this matchup (and I know this will piss off a lot of Greninja players), I would say that it's actually slighty in Ness' favor. Ness only has 4 or 5 actual bad matchups, I don't see Greninja even coming close to being as threatening as them. And I'm even one to say our matchups are worse than most Ness players would think (I still think Diddy is bad, and the Ness boards disagree with me). Ness wins in the air, at KOing, and deals more damage in general, and loses off stage and slightly on the ground.
55:45 for Ness is my impression, the lowest I'm settling for is even. There's just no way it's a bad matchup for me.