Super Mystery Dungeon has unfortunately won the place of 'least favorite entry in the series' for me. It's not a bad game. Far from that actually. It had many good aspects I am going to touch upon but I just seemed to prefer Rescue Team, Explorers and Gates more.
It felt good to have great characters again, something that Gates never failed at. Your partner had good focus and wasn't just some sock you had to embark in your adventures with. Although what Gates did right in my opinion is giving your character a voice: for the first half of PSMD, I felt as though my player was a mere puppet entirely pushed in the plot by my partner. It eventually got better but I couldn't help but dislike this mute aspect of the player. Supporting characters like the Expedition Society (which all had GREAT personalities and interesting involvment in the plot) and Espurr (I LOVE YOU ESPURR) were also very well built and were pleasant to interact with.
I knew something strange was up with the partner when the scarves gave us some overpowered temporary evolution and especially when she started reading perfectly ancient dialects. I initially thought my partner was actually another human. They kinda dropped the ball with the Mew reincarnation at the end. It felt a bit forced and out of nowhere. I also don't get why the partner had to leave (now THAT was something original I like to see) but the player didn't. Was my character expected to remain in the Pokémon world this whole time ? I'm still a human after all: making the partner disappear in blinding light does not excuse my foreign origins.
I did not like the partner's excentric and outgoing personality at first (it got better over time). I know it's something they've done all the time in previous entries, but the serious, collected partner is always something I adore seeing.
I loved how they immerged you in daily-life events at the slow beginning part of the game. The Pokémon School was very cute. I felt like a child again: it was a very comforting feeling.
However, being treated like a child the whole game was something I felt was unnecessarily annoying. Even in dire times, Espurr never was treated as such and she pulled some crazy things in the story (which, again, I adored). It would have been better if Ampharos and the other Expedition Society members acknowledged us as grown-ups as soon as we made it into the society. Although I will say Archen's protectiveness over us during the story was very appreciated.
And as for the story... It stands on a similar ground to Gates to me. It was a bit sloppy. The final boss being some kind of living negative matter was déjà vu (I cackled a few times at Dark Matter's sh*tposting dialog). I liked how they approached in some fancy way the underworld, though. But overall, there are many things that could've been handled better, like Krookodile's lack of actual important role (I can't believe nothing happened with him after everyone turned back to life, I was soooo expecting Archen to be captured or something), once again the immersion of Mew's importance in the story instead of blowing it up totally at the end, the player NEVER even remembering ANYTHING, even after the ending events... It was a good story but had plenty of space for improvements. I also dislike how the Serene Village plot seemed completely irrelevant to the rest of the game (except maybe building up the few important characters of Serene Village, like Nuzleaf and Espurr). Post-game just as lacking as Gates', which is a shame...
I want to end on the game's surprise effect: these freaking "[POKÉMON] WAS BAD AFTER ALL" moments that happened MULTIPLE TIMES in the story made my heart twist pleasantly on many occasions. I was suspecting Nuzleaf a bit from the beginning, so I was already prepared to take the hit, but Beheeyem and Espurr's "betrayals" PLAYED WITH MY EMOTIONS SO MUCH, especially Espurr's. Beheeyem was the most confusing and funny one though. I was all like "IS THIS A TRAP OR NOT, TELL ME, MONSTER!!". It was very predictible but I'll give the game props for toying with me a little.