Just finished watching this movie. I got to say... I liked it.
However, I got to say something: the plot should have been developed a bit more. Ok, I get it, the Genesect want to find home and Mewtwo wants to help them, since she knows how they feel. But it would have been better if Mewtwo's story was more different compared to the old Mewtwo's story. I have not many problems accepting the fact that Mewtwo has the same exact appearance of the other clone (since Mewtwo's design is that design and has no form differences, a part its Mega Evos, and they aimed to use a different Mewtwo for whatever reason) and that the fact that Ash has met one is left unknown, but they should have worked more in showing at least an explanation of why this Mewtwo is so similar to the other one. Sure, not matter what people would have cried nonsense and complained for whatever reason, but I would have appreciated them at least trying.
The ending was quite anticlimactic, but the sight of the Earth was breathtaking. It's a bit weird the way in which "Red" had an epiphany, but I've seen several times where characters said "That's my world!" while looking at the planet from far. It's quite clichéd admittedly and I would have appreciated that they used something else. I'm not going to lie, my very first impression was that Mewtwo wanted to kill herself along with "Red", but that would have been a bit out of character from Mewtwo's part.
Also, the (Italian) voices were really unfitting. Mewtwo sounded a bit too much like Virizion, the Douse Genesect voice was too childish and Red Genesect voice should have been a bit more robotic. Well, that isn't exactly a point, since all dubs are different.
Negatives aside, I liked the interactions of the characters. At times I felt very sad for Douse Genesect, with her wanting to return home. Also, I was touched when the "natural" Pokémon wanted to help the Genesect once they saw "Douse" protecting Ash, showing that there is a bit of good in those "killing machines".
Another thing that I liked was Mewtwo's personality. It was slightly different compared to the other one, with her being less hateful toward the humans and more friendly toward the natural Pokémon. That's something that I appreciated, since that sets her apart from the other clone.
Conclusion, this movie deserves a 7. I didn't find it as bad as most people claim, but it could have been better.