just hit the 20,000 mark last night by completing reach on legendary alone. I haven't tried to get achievements in the past i just sort of played the games and got them but now i am trying and my goal is to get to 100,000 before 2013.
Not high enough! Only at 26,795 at the moment, but I'm making an effort to go back into earlier games to perfect them or to get as many of the achievements as possible. Gotta be quick before the MP servers go down for some though.