Europa Park is certainly one of the best themeparks in Europe, and not just because they have the highest and longest roller coaster. In fact, it's not so much the thrillrides that make this park great. The park is devided into areas, each themed after an european country in detail. There are so many fantastic rides, there's plenty to see for everyone.
Also, Europa Park knows how to make the most of each rides capacity, there are hardly ever long waiting queues. A must see.