Comfortable Stays: Holiday Inn Express Belgrade - City
Very recent hotel, it is comfortable, clean, easily reachable from airport, and serves a good breakfast. Staff is friendly - if you like local wine, try to catch the manager at the bar, he might serve you an extra dose. It lacks restaurant / fitness / pool however, but with its ideal situation at walking distance of most attractions, it won't be an issue for a relaxing weekend.

Holiday Inn Express Belgrade - City - Large bed