Hi, i'm from belgium and i would say if you haven't been to plopsaland, you should go once. It is not the best park but it's a very nice and beautiful place to walk around. And i heard anubis is very very good.
i haven't been in the U.S so i only can say a few flumes from around here in europe.
The best one for me is indiana river (bobbejaanland), it's totally indoor, the drops aren't very high but they ar in the dark and you get wet most of the time you do it.
The worst one for me is river splash in bellewaerde.