First, the EU has improved the lives of many of its 500 million residents by gradually implementing a common market for people, goods and services. For many people, this means using the same currency in different countries, using their mobile phone "as if at home" while traveling, and having access to a larger range of goods and services. For the 3 percent or so who live outside their home-countries (a share slightly smaller than the number born outside the EU), the EU means a different life. For those living in their home countries, the EU gives them an outside option should their national government fail them. (Polish are the most common nationality living in other countries; Cyprus and Romania have lost the largest shares of their population.)
These freedoms are improving life for people who travel, stay in place and migrate. Some people complain about "foreign" people or habits, but I see these complaints as parochial scapegoating over deeper issues such as falling birth rates or economic development.
Let's not forget that the EU has not had a war between members, in defiance of Europe's history.
On the downside of the EU is the way that many nations prefer to "grab" rather than cooperate. Some examples include the French grab at agricultural subsidies, the Spanish fishing fleets continued destruction of local and foreign fishing stocks, and the way that the Germans and French forced austerity on Greece, Ireland and Portugal (with some noise about too-large-to-bully Spain and Italy). Those debtor nations should have just declared bankruptcy in the face of the consequences of their corrupt and foolish spending spree in the early 2000s, but their poor citizens were forced to pay far too much back to the French, German (and other banks) that lent them too much money.
Bottom line: The EU has done a lot for its citizens, but it could do with less crony capitalism and more bottom up aid.