Album: First Love
I love R&B, ballads, etc. It's not the first album I've heard of her, but it's the one that I find extremely nostalgic of the 90s. I loved the slow, steady, easy listening 90s era. The most number of my favorite songs below come from this album.

Songs:
1. Simple and Clean: It is the first song of hers that I heard, and it will be my favorite for a long time. Its position will probably NEVER change. I may have an occasional interest in another song, but this will always be number 1.

2-5 change positions very often but they are:
Kremlin Dusk: I don't really know if anyone has discovered the song's meaning yet, I won't definitely try. Musically it is one of my favorites, incorporating a slow ballad intro into an uptempo rock-influenced climax.
Show Me Love (Not a Dream): This song reminds me of Kremlin Dusk quite a bit. I love the dark aura that the song musically radiates. I tend to like power ballads more than regular ballads.
Final Distance: This is the most-played Utada Hikaru song in my iTunes library, with 1295 plays and counting. It, to me, is a very sad record because of its background. I especially love the ending "echo."
Movin' On Without You: The fastest song in my top 5. In fact, it is the fastest song in my entire top 10. I started to like this song because of UU2006 and I loved the dance-club beat they added into the performance. I like dance songs as well, but not as much as ballads.

6-10 change positions as well, though they probably never will go above 6 and below 10.
time will tell: I didn't really listen to this song before her WILD LIFE performance. After that performance, I really began to appreciate it.
光: One would thing that for a song that sounds like Simple and Clean, 光 would place higher. It probably did not because of the difference in language and how she sings it.
First Love:The song and the album in the top 10? Preposterous. Not really, because I love this song. Once again, ballads have the power. I listen to the English covers as well, but I don't like them as much as I do the original one.
Sunglasses: The intro reminds me of the music in my earlier childhood. I used to always listen to R&B when I was a child, and my tastes reflect on this very R&B song.
COLORS: Hey, it's that song that was bundled with Simple and Clean! But in all seriousness, this song is very Oriental-sounding, and it sounds extremely different from the sounds in ULTRA BLUE which is my next favorite album.

Heart Station isn't very well represented here, but my favorite song from that album is:
テイク 5: This ethereal-sounding song about death is extremely entrancing. I appreciate the abrupt end to the song because making it fade to black would make its meaning less... meaningful. I would place it at 10-15.
This Is the One isn't on this as well (barring the re-release of Simple and Clean), but I do have a favorite on that album:
This One (Crying Like a Child): This song is the most played song from This Is the One in my iTunes library at 412 plays. I simply liked the song because of its R&B vibe + ballad slowness. This would go under 10-15 as well, but I would like to think that it's number 11.