When his birthday comes (October 10) he's gonna be 17 but right now he's 16. Which means:
Sakura=17
Sasuke=17
Sai=18
Kiba=17
Hinata= still 16 (birthday December 27)
Shino=17
Ino=17
Shikamaru=17
Choji=17
Lee= still 17 (birthday November 27)
Tenten=18
Neji= (deceased but) 18
So as stated above the others (except Hinata) are older than Naruto b/c Team Gai + Sai (for now except Lee) are a year older and the others birthdays must've came so which makes them older only by months. (again except Hinata)
Actually, it's not that complicated, nor difficult to believe in. You can check out my Timeline, there is a link in my Sig. There you can find more detailed informations. :yeah: