I'm an atheist and, believe it or not, I'm a good person. You can't really make a generalization like that about people you don't know. By the way, you're not the only people who feed the hungry in Africa or do other good things. Here's a list of some atheists you should know:
A. Philip Randolph - African American civil rights leader
James Randi - founder of the James Randi Educational Foundation
Zackie Achmat - South African anti-HIV/AIDS activist and founder of the Treatment Action Campaign
Bill Gates - donated over $30 billion to charity
Barry Manilow - donates money to political campaigns
Douglas Adams - evironmental activist who campaigned for endangered species
Alan Cumming - AIDS activist
Jodie Foster - teaches her children to respect all religions
Benjamin Franklin - invented fire departments, electricity, bifocals, etc; also charted the Gulf Stream and worked to abolish slavery
Galileo Galilei - found out the sun is in the center of the solar system (was ironically placed under house arrest by the church because of this "theory")
I don't feel like putting all the Christians on here. Maybe I'll do it later, but here's one BIG one:
George W Bush - said God wanted him to go to war with Iraq
And finally, there are a lot more Christians in prison than atheists. And by Christian, I don't mean they found God while in prison; I mean they were supposedly Christian before getting arrested.