I may have only been once to Europa but it shot to my number one park for so many reasons. We spent 6 days there with one night in every hotel
(something I highly recommend for anyone visiting for their first time - called the hopping pass) which was an absolute joy.
I think the reason why Europa excels to the top is quality. They may not have the largest selection of 'high thrill' coasters but to me that doesn't matter, Wodan & Blue Fire more than meet my needs for thrills with Wodan being superb in my view. The balance of the park is fantastic and the theming is world class.
If I were to compare some of the parks I have been to and surmise what I like best about them all...
Alton - Coasters
Phantasialand - Theming, Rides and Hotels
Portaventura - Coasters
I love Europa for the rides, coasters, operations, staff, service, food, drinks, hotels, theming, escapism, variety/offering of rides and value for money. I basically love everything about the place and everything they offer is just at a higher standard than any other park I've been to. There's a reason why "blank cheque for Roland" exists because people don't mind spending a lot of money if you want to, because the return service is exceptional.
It beggars belief how anyone can find the place overrated, sure, everyone is entitled to their opinion and not everyone may like the place as much as me and others, but overrated? I just can't see it. People must have ridiculously high standards if Europa is ever classed as overrated.