Ummmm.... The greatest things to achieve are:
Love, to have great affection with someone, to always have someone beside you, who understands you, takes care of you and makes you happy and of whom you take care and everything... It is wonderful... It gives a great, wonderful, warm feeling...
Fame, yes... I just said fame. But i don't mean like a superstar's fame, but like... just do that your memory would stay after you, in the mind of people close to you... I think it is importand to leave something behind... At least it is for me.
Ummm... those would be the greatest things I can imagine ^^