I have 2 questions about the xbox 360,maybe you guys can help?

1. how limited are the limited xbox360 games? I have the feeling even limited editions are common with 100.000 copies made AND are some limited editions more rare then other? pal or ntsc?

2.Is it possible to get 100.000 achievement points? Is saw many people leave there xbox 360 profile under there username and saw some big scores like 13.000 and even 44.000+ but 100.000?