You know how the feeling of completing one side of a rubik's cube? that is how you would feel after watching S;G. But how about completing all sides of the rubik's cube? that is what you feel after you watch S;G0.
Before I go in deeper I question people in the review section. Why would you say this is a "what if" arc? this is definitely not. Everything is connected from S;G and S;G0 making this just a completion of S;G or what you would call a "True ending". Without this, the ending of S;G wouldn't even exist in the first place. Get your facts right please.
While S;G0 might be a sequel to S;G, it is actually not. S;G0 is just a detailed explanation of how the story evolved into the final episode of S;G. Remember how at the ending of S;G, Okabe got a video of his future self? I'm pretty sure we all are curious on the story of that future self Okabe and S;G0 is the answer. So for people expecting a sequel to the original S;G, sorry to break your heart but this is not. (I mean we already have the movie sequel and ova, what else is there to do a sequel with? A sequel after that would only break the perfect ending of this masterpiece)
So how about S;G0 itself? S;G0 paced really slow at the beginning. For someone who re-watched S;G and binge'd S;G0, it was really irritating. There were character that suddenly popped out and we were (kinda) forced to accept their existence. The story itself as a standalone is mediocre. However, if you see the big picture, this 2nd season was meant to support the original S;G and when you see the whole story, it was really satisfying especially the 3 last episodes, which although was a bit rushed, was really worth it after all the agony of waiting.
In the end, the most important part of S;G0 was to get to the last 3 episodes. However, I still think that they could've done better on the beginning and the end, as the beginning is slowly paced and the ending was rushed, they could've balanced it by compromising on each. I also find that the art and the sound itself really lacking, which probably is a letdown to some of us. Another thing that would be wrong about this is how Kurisu's voice in S;G0 differs a bit with the original S;G albeit being the same voice actor. Feels like she forgot Kurisu's personality or something.
To end this, the true timeline of the whole S;G would be:
-Season 1 from ep 1 to midway ep 23
-Ep 23 beta OVA
-All of S;G0
-Second half of S1 ep 23, then 24+25
-Cognitive Computing OVA
-Deja Vu movie
However I wouldn't really recommend watching it like this as it would ruin the whole fun of this series. Also, to watch S;G0 I would recommend watching from the beginning of S;G (The first season) for a better experience. After finish watching S;G0 you might wonder how some facts in the end contradict with the rules of the S;G itself. For that you might want to check the last ep discussion (there's someone who explained about it) because as I said before, the ending itself is a bit rushed and you might have to think with your own about how it can conclude to that.
TL;DR if your brain can't handle processing the original S;G "puzzle", then you wouldn't have fun deciphering this whole S;G0 because the theme of both S;G and S;G0 is connecting the dots.
