Catalonia (and some of the mediterranean) is interesting, the north is pretty and green, and the south is very culturaly rich and has amazing arab influence; but everything inbetween (including Madrid) is bland and boring.
That's why I think Summer Olympics are a big reach. Madrid has no iconic monument, interesting landscape or special athmosphere, so it would look very random and with no personality.
Other citys like Valencia, Seville, Zaragoza and Bilbao are more beautiful and interesting and they could hold smaller events like European Games and do an amazing job... Or even Madrid. But just not the Olympics.