Obama's legacy has good spots and bad spots. In the future, his drone policy is something that may be viewed as a stain on America much like America's cold war meddling in South America that caused misery and bloodshed for millions of Latin Americas.
On the other hand, Bin Laden is dead, we didn't start any new wars, the US left Iraq, and several regimes changed to democracy in the Middle East without the US military getting heavily involved.
Obama's Justice Department has successfully shed light on patterns of police misconduct in several major cities and has mandated reforms. Yet, Obama and the DoJ ignored a landmark report on forensic science that could've exonerated thousands of wrongfully convicted and prevented wrongful convictions in the first place.
Net Neutrality won the day under Obama, yet he has done precious little to roll back pervasive surveillance and indeed has strengthened it.
In the fullness of time we'll see if Obama's legacy is ultimately viewed as negative or positive. And a lot of that depends on individual perceptions and what issues are important to you. Not to mention that feelings about his legacy will depend a lot on the quality of presidents succeeding.