VideoGame This game is amazing and the final battle is astonishing! (SPOILERS)
I honestly think Mario & Luigi: Partners in Time is the best Mario & Luigi game, and this coming from someone who fondly grew up and loved Mario & Luigi: Superstar Saga.
What beats SS is the story. The story is very dark for a Mario game and darker than the other games where we have an actual hostile alien invasion in the peaceful world of Mario and the Mushroom Kingdom. A force greater than Bowser that wants to conquer Mario's world and kill whoever gets in the way. They murdered Toads and destroyed many innocent lives mercilessly. Even worse, this is when Mario and friends are just toddlers! Mario, Luigi, and their past selves team up to fight off the alien invasion, and this means that the aliens will kill anybody, even innocent children!
The Shroob Queen's menacing final form, the desolate background with dark and thundery skies, you're on a small floating platform with nowhere to run, Peach is passed out and no longer able to help you out, and when Mario and Luigi pass out, the final hope of the world is Baby Mario and Baby Luigi fighting against a giant tentacle monster alien! All of this combined with this chilling and ominous final battle music by Yoko Shimomura makes for one of the best final battles in a Mario game or RPG I have ever played!
I love playing this battle over and over and I always get chills when I get to this part because I desperately have to keep the adults alive because I get massive chills and super nervous when I have to use little innocent babies to fight and they can very well DIE. Plus, when one of the babies die and the other baby picks him up and carries him, my heart breaks so much...Mario and Luigi never give up on each other, not even as babies.
Superstar Saga and Partners in Time are the two most memorable games in the Mario & Luigi series and you don't want to miss these two for your first time playing.
VideoGame Doesn't hold up
I played this and Mario & Luigi: Bowser's Inside Story forever when I was a kid. They were my quintessential Mario Rpgs and I've likely had more playthroughs of them than for any other game. They were possibly the most played games on my DS, so I have great nostalgic memories for both of them.
However, unlike Inside Story, which still holds up today and is one of my most beloved games of all time, this game reveals a myriad of emptiness and broken potential once I looked at it again.
Firstly, the Time Travel aspect of the game is severely underexplored. While Inside Story had the Bros interact with Bowser's body in unique ways, creating interesting solutions and empowering Bowser through engaging minigames, Partners in Time barely has the time travel affect the gameplay at all. The areas look and feel just like any other Shifting Sand Land or Lost Woods, with nothing making the levels stand out as "in the past". This is compounded by the fact that the Bros never visit any location in the present except Peach's Castle, not allowing contrasting between the past and present world like how The Legend of Zelda: A Link to the Past did with their Dark World, and there only being two time periods you travel between. Instead of going back through varied time periods and meeting the founders of the kingdom or your ancestors like in Chrono Trigger, all you do is meet younger versions of existing characters, which brings me to my next complaint.
The babies are annoying and the worst combat gimmick out of the five games in the series. They don't add anything like the elements, Bowser, dream world, or Paper Mario. They are merely carbon copies of the adult Bros with different button inputs. The puzzles involving them are decent but not great, and hearing them crying over and over again is a bit grating.
As for level design, it feels like you just go in a straight line a large amount of the time, and there are very few sidequests or anything that would make you want to go back to other areas. Once you've gone back through the time hole to Peach's Castle from an area, that area has no purpose anymore, and since you never return to any area after completing it, they are all easily forgotten. While I do like some of the puzzles and enemies, there's nothing extra to do in the levels and no bonus for full completion.
In conclusion, this game is definitely a mediocre Sophomore Slump, and honestly even Mario & Luigi: Paper Jam is better, as it has far better combat and more things to do besides the main story, incentivizing exploration.
Still leagues ahead of Paper Mario: Sticker Star though.