i feel the same, but it may be nostalgia. i only played through the entire trilogy in like 2018, way after my first playthrough of the first prime. prime 2 has a very different feel, more like a constructed game world than something that fits together naturally. it's also a lot less colourful and the dark/light thing feels sort of slapped on.

prime 3 is all over the place. i haven't played 4 because i don't want to buy a switch 2.

i think the evolution of the prime series served to have it fall more in line with the original vision for the character of samus aran, which famously is very different in the english-speaking world due to a mistranslation. the word "bounty hunter" should have been translated as "mercenary". if that hadn't happened, metroid prime would probably have been a lot closer to halo.

the first one is the only one i'd recommend (and it's remaster)

I do like all the trilogy (there's only 3 of them right? Right).

It's true only the first one has that classic connected world, though IMO 2 had fairly big areas with multiple paths so it felt close enough.

3's map design was a bit weak but I liked the new gameplay around motion/pointing (though I still prefer the gamepad for 1 and 2, they were not made for pointing and the wii controls suck for those).

The game that may or may not exist made me angry. There are some decent parts, but they're lost in an ocean of annoying shit. Especially a completely useless central area, extremely linear design, an uninteresting antagonist and cringey assholes spamming you with terrible dialogues for the full game. Fuck you, Myles MacKenzie.

I had metroid prime 3 for the Wii and i have good memories of it, and that (incredibly) the motion controls felt very natural to use

I played the first 3 and only all the way through 1 and 2. 3 got stale really quick for me and I didn't play through more than half of it. Haven't touched one since, so I can't say if they got better again, but I also think Prime 1 was the best one of that series I have played.