Sure, unemployment is down and GDP is growing. But Obama was unable to give back the confidence which the financial crash sapped from the American public.
The wars are still being fought in the middle east, despite promises to end them. They've mutated, but are still happening.
What's more, Obama pushed his lefty agenda, and believed (or chose to believe) that he was in fact being unifying.
Obama was full of hope, but was ultimately disappointing. He'll be remembered, but not because he was 'good'.