Honestly, depending on the website, every hotel is going to have a couple bad reviews. People get angry when they don't get what they want, no matter how unreasonable, and then they retaliate by putting bad reviews. Angry people are more likely to write a review than happy people. What you really want to check for is if the hotel responds to those reviews, and what tone they use with those responds. You have to use intuition to sort out the legit bad reviews vs. the bogus ones. Oh, and compare the pictures the hotel puts up vs. what reviewers put up, the difference will tell the story. Hotels specifically for cedar point, I can't personally help you with, but I know those websites will give pricing. I think what you should be asking is what is the best option for your budget.
Also, I know you and I are very different people, but for me personally, the only way I'm going to care about an indoor water park and not Cedar Point is if its raining. One of the more well known parks in the country will win over a couple of slides I can experience at home every time. And if you really want the indoor water park experience I am pretty sure it'll be better at the Great Wolf Lodge or Kalahari, who both have a much larger focus on the water park. Both companies have resorts near me, and while I haven't stayed in either, I have toured both, and they are amazing properties, I can't imagine the Sandusky ones being any different.
What are these for?