Favourite to least favourite:
1. Pansies
My favourite overall, have been my favourite as long as I can remember. I've always liked them in real life, too! Maybe childhood Animal Crossing memories have something to do with that...
I reset my second island specifically to have them as natives; I love island-hopping and seeing pansies everywhere.
(too bad my second island was founded less than a month after the infamous 1.2.0 update that removed the hybrid islands...
)
I also prefer the newer, darker purple over the pink/purple pansies from the Gamecube era. However, it would be nice for the earlier purple design to one day return, maybe as a 'pink' option!
2. Cosmos
My native flower on my primary island, did not even know about native flowers at the time! I've had a garden of them arranged in a pattern in front of my house/on my flyover since summer 2020. Even all this time later, it never gets old to boot up ACNH and my first moments are walking outside, right into the huge cosmos garden.
(They could really use some cooler palettes, though. I sure do miss the blue cosmos from the Gamecube era.)
3. Windflowers
I didn't expect to like these as much as I did, but seeing as I love pansies, their dark centers appealed to me. I love their darker options, and I even like their pink option, which is a rarity for me.
4. Roses
They're about middle of the road for me. They're versatile because roses, the dark shades are nice, and I'm a glutton for punishment who spent hours on that one ACNH flower genetics website and developed a long-winded, yet foolproof method for my sibling and I to breed blue roses. I think in total it took about six to seven months?? But definitely worth it for 2-1-2-0 black roses.
(Oh yes, who can forget how ridiculously campy (in a good way) the gold roses are? Almost forgot them!)
5. Tulips
My secondary flower in ACNH because of starting in March. They're fine but I think I prefer others more. At least they have a black option, so
(unfortunately, this was the only pre-1.2.0 hybrid island I was lucky enough to see in person. I would have preferred to behold cosmos hybrid island, given my options, but RNG gonna RNG.)
6. Mums
They're decent, I suppose, but they're just a little too bright and candy-coloured for me to find a use for them. However, the green is a nice option that none of the other flowers have, so they found a place on my island from that alone.
7. Lilies
As a whole, I prefer these over the mums. But the mums having a unique colour to them inched them up just barely. I also agree that these would benefit from a 'harder' hybrid step; these crossbreed very easily and quickly, and I personally prefer the challenge.
8. Hyacinths
Ehh, I find these boring. Back before Leif was updated into ACNH, my sibling brought me some hyacinths from cleaning up a friend's flower mess. They lasted about...two hours on my island before I went 'ehh' and removed them. They really just don't work for me, and despite them having blue/purple options, I prefer almost every other flower's blue/purple. I'd even prefer violets, which were at the bottom of my totem pole in ACNL.
uhh tl;dr: I love pansies, prefer darker shades, and do not like hyacinths.