Hoo boy, Gen 7. I will divide my assessment of Gen 7 into different sections in order to make this comprehensive take more readable. The game I will review in this will be Moon, with some references made to the Ultra games.
Starting with the region.
Let me be blunt here, I think Alola might be the best region out of all the regions based on western locations... the only one coming close to snatching that title would be Unova. The lore, the customs & the aesthetics are exactly what you'd expect out of an island tour of Hawaii. And while it still has the out-of-nowhere desert as well as one of the shortest pre-Pokemon League dungeons in the hallway that is Mt. Lanakila, I think that doesn't really take away from the region itself as much as one would think.
How does it compare to the entire franchise? I'd say aggressively in the middle of the pack alongside Unova & Kalos.
Pokemon lineup.
I don't like pokemon lineups that make the game rely on previous generations to be complete. It's not even that the dex is to small or insignificant, 88 new pokemon sounds like a good value...until you find out 25 of them are reserved for post-game or events due to them being either legendaries, UBs or MYTHICALS. That's 28,5% of the pokemon out of an already smaller pokemon lineup that you're not going to see until late or endgame. And no, I don't count regional variants as 100% new content, though it is appreciated by those with nostalgia regardless.
This leads into the issue I have with this regional dex, the recycling of the same pokemon from gen to gen in regional pokedexes. I get it, you brought pokemon like Gardevoir, Gengar and the pseudo-legendaries back for this game for popularity reasons, GF. It made the pool of available pokemon in gens 4, 6 & 7 feel homogenous as a result, which is a pity since the pokemon introduced in Gen 7 were actually better than average for the most part in terms of aesthetics, lore, habitats they are found in as well as gameplay if you ignore the speed problem lot of them seem to have. In fact, out of all the supplementary pokemon lineups (Gen 2, 4, 6, 7), I may like this one alongside Gen 2 the most.
Performance & gameplay.
I ain't sugarcoating it, this game is slow and in rare occasions even had some frame rate issues. It's clear to me 3DS was not exactly made to handle stuffing a bunch of moderately detailed 3D models into a single cartridge. Though not as prevalent of a problem here as in D/P, I never thought I would see loading screens last more than a few seconds on a Nintendo console.
Next, lightning rounding new features: Z-Moves? It's just another delete-button you can use once per battle. Battle Royale? If you wanna see the game chug, you come here. Poke Pelago? You gave me the most convenient features in a single package, best feature in the game. Type effectiveness displayed when selecting move? Because nothing's better than openly promoting pitfalls while failing to properly explain mechanics like STAB that are arguably even more important than type effectiveness. Hyper Training? You're not using this unless you like competitive battling or are a Battle Tree masochist. Ride Pokemon? No more HM moves, hooray.
Lastly, the trials that are supposed to replace the gyms as the pillars of progression. I don't feel a difference. You're still contending with a single task or a gimmick, proceed to beat the stuffing out of a boss and then walk off towards the next one. And the trial bosses... kinda just keel over if you have at least a small clue of what you are supposed to do, with the exception of like one or two trials in the game like the Lurantis one apparently.
Characters & Music.
The music sounds very relaxed because muh tourist trap. That being said, this soundtrack ain't bad... despite some of the pieces feeling unmemorable. There are some winners here like the evil teams' themes, Lush Jungle, The Poni Island part of the game or the Tapu theme. I seem to have some trouble remembering the route themes though, probably because they feel sort homogenous to other route themes in the franchise.
In terms of characters, Pokemon franchise has often relied on aesthetics & first impression to carry them at the cost of story significance or character development. The problem I see here is that you don't interact with most of these characters enough for you to become attached to them, and whatever interaction you get suffer from a certain problem I will get to in a moment. And the Ultra versions? The story was already not remarkable in game industry standards, you did not need to retcon the story to make it even worse.
That problem being how much of that characterization as well as story beats lie within abundant exposition. There's a certain well-known advice of "show, don't tell" that is very relevant in terms of this generation's storytelling. And when all the interesting stuff starts to happen at pretty much the final third of the game or so, with this generation being the first one to bring the "second twist villain group"-trope into the formula, I found myself getting bored if not annoyed with the game instead of immersing myself into it. This generation holds your hand throughout the majority of it to justify its story beats... and it doesn't work. The reason the mainline games' stories got away with playing so safe when it came to storylines was because of said stories serving the setting of the region more than standing on their own merits.
Overall.
As much bashing as I did on this generation, it's... okay? If you can bear with the exposition, the slowness of the game or the fact the mainline games haven't really changed that much if at all over the years, you can play Gen 7 & not regret your life decisions. That being said, it doesn't hold a candle to Gen 2, 3, 5 or HG/SS. Gen 7 was also where the formula was starting to show its age.