In terms of gameplay, this one improves on many things from Sun and Moon, and adds a lot of cool features and new Ultra Beasts. However, the story is just a beat for beat retread of Sun/Moon except worse, downplaying and dumbing down certain character's roles. All in all, not much here that makes it worth playing over the originals.
It's really good. The Island Challenge is way better this time around than in the original SM and the game is truly, legitimately challenging to play. The story is in some ways a step down from the original Sun and Moon, but it more than makes up for it in the fun content it has to offer, which this game has quite a bit of. It's unfortunate that it came so soon after OG SM, if only they had waited another year to release this it might have been a bit better received.
most of my criticisms of Ultra Sun and Ultra Moon are similar to Black 2 and White 2 but this game has Mantine Surf and that's legitimately fun and the postgame Rainbow Rocket stuff is cool so I have to rate it just a little higher
that being said they botched the story hardcore, which is a shame because it was one of the reasons the originals shined. Ultra Necrozma is without a doubt the worst boss fight in this entire series, and that's not even talking about how they made one of the coolest Pokemon designs into some boring light dragon. I'm not looking forward to 5 years later when people try to convince me this game is on par or better than the original Sun and Moon, which is the pair you should buy instead of Ultra Sun and Ultra Moon
that being said they botched the story hardcore, which is a shame because it was one of the reasons the originals shined. Ultra Necrozma is without a doubt the worst boss fight in this entire series, and that's not even talking about how they made one of the coolest Pokemon designs into some boring light dragon. I'm not looking forward to 5 years later when people try to convince me this game is on par or better than the original Sun and Moon, which is the pair you should buy instead of Ultra Sun and Ultra Moon