Good:
- Economic recovery
- Same sex marriage (not directly an act of Obama's, but occurred under his Presidency)
- Osama Bin Laden
- Iran deal
- Cuba normalisation of ties
Bad:
- Guantanamo Bay still open (not for the want of trying)
- Record military aid deal to Israel
- No gun control (again, not for the want of trying)
Considering the impediments he has faced (i.e. Republican controlled House and Senate that completely oppose everything he tries to do and all of his attempts to work together), he has done a pretty good job. He does, however, have to take some responsibility for Trump's victory, which was almost a vote on his 8 years in power (as Hillary was largely seen as a continuation of Obama, but she was mired with scandals and a terrible candidate, so I wouldn't put too much blame on Obama for her failures).