I played all the games so far around their release, but I don't think I've revisted them since. So they've all kind of blurred in my head as one experience.. Playing Pikmin 1 on the switch, though, I was struck by how focused and small (Ironically? Appropriately?) it felt. You don't have the caves or giant trash as treasure, you just have 30 days and 30 ship parts. And of course, the 3 standard pikmin types, with very straightforward uses. Most of the enemies can be defeated by just throwing pikmin at them, recalling pikmin when they wind up for an attack, and maybe making sure you use yellow pikmin if it's tall, or blue pikmin if it's near water. The bomb rocks are the most fiddly thing to manage, but they also add just a little texture to battles and to opening up more efficient routing in, basically, one of the five levels.
I've noticed a lot of people bring up the time limit as a stress point when talking about Pikmin 1 (ie on a recent Remap Radio), but I think not only is it generous, the 1:1 ratio of objectives to days makes it easy to understand how generous it is once you get started. You don't have to do any math to figure out if you're on schedule, just get one part per day, and as long as the number of parts you have is greater than the number of the day you're ahead of schedule. I only had one day I didn't bring back any parts, but I was several days ahead by then. I'm sure it was more challenging for some people, especially kids who obviously the game was meant to appeal to as well, but I still feel like the time limit is meant as a motivational threat, something to make you think about efficiency and not just call it a day as soon as you complete one objective, instead looking for how you can set up for the next day (and potentially getting you in trouble if you try to multi-task too much and have to run around the map collecting your little guys before sunset).
The levels themselves also felt smaller and more focused than I remember these games being. Especially since there's really three big levels, then the starting area (with a treasure you need to come back with blues to get, and some optional bosses that funnily enough, I didn't see at all until the creature montage at the end) and the final boss arena.
And of course the atmosphere is so different from the other games. Olimar is stranded and afraid he's going to die, he has no communication with anyone else, the only text you get is from his thoughts popping up during play and his journals at the end of the day. There's jokes, especially about the various ship parts (like, "I don't know what it does, but it sounded impressive and was very expensive!"), but it's tempered by his actual desperation and connection with the pikmin as something he doesn't really understand but which he can connect with and see as a lifeline. Not that every cute Nintendo game needs an undercurrent of "oh god I'm going to die here, alone", but as a personal preference, I really enjoyed it.
Also, now that I've started into Pikmin 2, having the game constantly be interrupted by a snarky spaceship is waaaaay more annoying than having a full-screen pop-up that just says, "Hmmm I think maybe if I hit the A button, I can throw these creatures!"