According to poll conducted at Biglobe website, anime fans have voted the characters from the anime series Mahou Shoujo Lyrical Nanoha as the best magical girls ever.

Out of the top 25, 11 of which came from the anime series, Lyrical Nanoha with main characters Fate T. Harlaown, Takamachi Nanoha and Yagami Hayate rank as number 1, 2 and 4, respectively. Akemi Homura from Puella Magi Madoka Magica is number 3.

Rankings:

1. Fate T. Harlaown (Mahou Shoujo Lyrical Nanoha)
2. Takamachi Nanoha (Mahou Shoujo Lyrical Nanoha)
3. Akemi Homura (Puella Magi Madoka Magica)
4. Yagami Hayate (Mahou Shoujo Lyrical Nanoha)
5. Vita (Mahou Shoujo Lyrical Nanoha)
6. Kinomoto Sakura (Card Captor Sakura)
7. Reinforce II (Mahou Shoujo Lyrical Nanoha)
8. Teana Lanster (Mahou Shoujo Lyrical Nanoha)
9. Takamachi Vivio (Mahou Shoujo Lyrical Nanoha)
10. Subaru Nakajima (Mahou Shoujo Lyrical Nanoha)
11. Caro Ru Lushe (Mahou Shoujo Lyrical Nanoha)
12. Kaname Madoka (Puella Magi Madoka Magica)
13. Lili Strosek (Mahou Shoujo Lyrical Nanoha)
14. Mami Tomoe (Puella Magi Madoka Magica)
15. Sakura Kyouko (Puella Magi Madoka Magica)
16. Millhiore F. Biscotti (Dog Days)
17. Miki Sayaka (Puella Magi Madoka Magica)
18. Signum (Mahou Shoujo Lyrical Nanoha)
19. Lina Inverse (Slayers)
20. Shirai Kuroko (To Aru Kagaku no Railgun)
21. Minky Momo (Magical Princess Minky Momo)
22. Nijihara Ink (Moetan)
23. Furude Rika (Higurashi no Naku Koro ni)
24. Akazukin (Otogi-jushi Akazukin)
25. Kuroi Sumi (Moetan)

[Source]