Best things: Obama's winning the presidency, the Olympic Games actually went off without major glitches, and gas prices actually fell to a reasonable level by the end of the year.
Worst things:The economy tanked and went south, banks failed, millions of people lost their jobs and had their houses forclosed, there was a massive earthquake in China which killed thousands of people, we had two major outbreaks of foodborne illness, one of which is on going as we speak and has already killed 8 people, and we lost some famous people for various reasons, some of which died long before they should have. There was also the Israeli- Palestinian war, the Iraq and Afghan wars, the Chinese crackdown on Tibet, the hurricaine in Mynamar ( also called Burma) which killed thousands of people, Hurricanes Ike and Gustav in the US, and massive wildfires in California.
I wouldn't call 2008 the greatest of years. There was more bad than good, if you ask me.