This is my ranking of ayu's 50 singles to date:
01. &
02. SURREAL
03. A
04. INSPIRE
05. Mirrorcle World
06. M
07. evolution
08. Dearest
09. BLUE BIRD
10. Rule / Sparkle
11. H
12. Free & Easy
13. glitter / fated
14. Startin' / Born to Be...
15. Boys & Girls
16. Moments
17. talkin' 2 myself
18. Days / GREEN
19. Daybreak
20. fairyland
21. CAROLS
22. No way to say
23. Endless sorrow
24. HEAVEN
25. STEP you / is this LOVE?
26. SEASONS
27. WHATEVER
28. Fly high
29. kanariya
30. You were... / BALLAD
31. Depend on you
32. Voyage
33. UNITE!
34. forgiveness
35. Trust
36. Bold & Delicious / Pride
37. vogue
38. MOON / blossom
39. LOVE ～Destiny～
40. L
41. NEVER EVER
42. crossroad
43. TO BE
44. Far away
45. For My Dear...
46. appears
47. Sunrise / Sunset ～LOVE is ALL～
48. poker face
49. YOU
50. AUDIENCE
----------------------------------
If you need to refresh your mind:
http://en.wikipedia.org/wiki/Ayumi_Hamasaki_discography