In Naruto Shippuden: Ultimate Ninja Storm 2 for the PS3 and Xbox 360, you can unlock several characters by simply earning SP during your battles.
Here is a list of the characters you can unlock with SP, and how much SP you need to earn to get them.
Chiyo – 140,000 SP
Deidara – 100,000 SP
Hidan – 260,000 SP
Itachi – 400,000 SP
Jiraiya – 440,000 SP
Jugo – 360,000 SP
Kabuto – 220,000 SP
Kakuzu – 280,000 SP
Karin – 340,000 SP
Killer Bee – 540,000 SP
Kisame – 120,000 SP
Konan – 480,000 SP
Lars – 600,000 SP
Minato (Fourth Hokage) – 580,000 SP
Naruto (Rasen Shuriken) – 300,000 SP
Naruto (Sage Mode) – 520,000 SP
Orochimaru – 240,000 SP
Pain – 500,000 SP
Sai – 200,000 SP
Sasori – 160,000 SP
Sasuke (Taka) – 560,000 SP
Sasuke (Kirin) – 380,000 SP
Suigetsu – 320,000 SP
Tobi – 420,000 SP
Tsunade – 460,000 SP
Yamato – 180,000 SP