I don't like achievements because they reduce the number of noteworthy things I can do while rarely giving me ideas for cool stuff. They rarely include cool self imposed challenges. Places where they do work are games like Geometry Wars 2, where it gets you to do things you wouldn't normally think of as a challenge, like the "Wax on Wax off" achievemnt.
Ultimately everyones life is pointless, because, eventually, you will die; and even if you are remembered for a long time as a innovator or a hero, at some point, the earth or the universe will come to an end and every memory of you will be gone; with every effect you've had on the universe have so little impact it'll be almost unnoticable. Achievements give us something to do while waiting for that to happen ^^.