Being the richest man in the cemetery doesn't matter to me. Going to bed at night saying we've done something wonderful... that's what matters to me.

This quote is talking about what is important to the speaker. The speaker does not care about being the richest man in the cemetery (a cemetery is a place for burying the dead). Instead, what matters to the speaker is feeling that they have done something wonderful. In other words, the speaker values feeling a sense of accomplishment over having a lot of money.