The story here is complicated, so I will break it into parts:
1. Afghanistan: Obama portrayed the Afghan War as the “good war” during the 2008 campaign, partly because he believed it, but mostly out of political opportunism. Once in office, he found himself unable either to make the Afghan government work or to solve the conundrum of Pakistani double-dealing. He tried to force the Afghans to address their problems by withdrawing, but the Taliban only gained strength, and the withdrawal had to be reversed in part. Today, Afghanistan is a quagmire, with no end in sight, just as it would have been if anyone else had been President.
2. Iraq: Obama was unable to persuade the Iraqi government to permit our troops to stay under acceptable terms, so he made lemonade out of lemons and completely withdrew. The Iraqi government, to no one’s surprise, proved to be sectarian, corrupt, and inept; anyone who thinks that the continuing presence of American troops would have changed things is kidding himself. The US initially underestimated the strength of IS, but used the ensuing crisis to its advantage; a new and more friendly government with more willingness to fight was created. By the end of Obama’s term, IS was on the verge of collapse in Iraq, but none of the underlying political problems had been solved, and more troubles with the Sunnis and Kurds loomed ahead.
3. Libya: Obama was pulled into Libya against his wishes by more enthusiastic European governments. The war was won at very little cost, but the country collapsed into warlordism in the absence of an occupying force on the ground. IS intervened, but was crushed. Would you rather live with anarchy or tyranny? Different people would have different answers.
4. Syria: Having possibly missed an opportunity early on to bring down the Assad regime, the Obama Administration took the (unspoken, but realistic) position that an acceptable negotiated solution could only come from a balance of power, and behaved accordingly. The Russians and Iranians upset these calculations by escalating the war beyond the administration’s willingness to fight. Instability in Syria resulted in a refugee crisis that tore Europe apart, and contributed to terrorism at home, as well. In light of the high price of passivity, would a more aggressive approach have worked better? We’ll never know; the only conceptual alternatives were the Libyan approach (limited intervention followed by anarchy) or Iraq (occupation), neither of which was likely to be welcomed by an American public that was sick of wars in the Middle East.
All in all, a mixed bag.