I'm still not entirely clear on what you think is off in the ratings. Your first comment implies that not all the games are overrated. Your next comment says that the 5 star rating is too high, and your earlier comments say that other ratings are too high. So is there any rating that's correct or too low in your opinion? Or is the rating of every game you've tried too high? I would again suggest that if you think the ratings of all the games you've tried are too nigh, maybe you are misunderstanding the intention of the ratings. It's all relative. Genrally 4 stars just means better than 3 stars, and 3 stars just means better than 2 stars and so forth. If you use the rating system like that, it might work better.
I do admit (and I believe I have admitted in the past) that even in my own opinion it's hard to come up with a single fair rating for each game, and if I rated them again, there's a good chance the ratings might end up being somewhat different because it's mostly a subjective rating system (my opinions). So I will tell you why some of my opinions are what they are, and maybe you can compare them to yours to help me understand more about what you think of the games and the ratings.
I tend to put a lot of weight on gameplay. I really like games that last a long time and/or tell a long/good story. I like games with a lot of variety and a lot of choices and freedom. Ethereal Peace is one of the best games in the listing in those categories I think. That's why it has 4 stars. So why did I rate Rolly the Purple Ball so high? Well, I value more than just gameplay and story. I also like clean design, nice graphics/animation/scrolling and pleasing sound effects and music. Naturally, since I designed all the graphics/animation and sound, and composed all the music for Rolly the Purple Ball, they are to my taste. And since I am obviously very familiar with how the kit works, I knew how to design the game to work very cleanly without allowing the character to get stuck on any corners or fall through platforms, walk through solids, or have difficulty fitting through narrow passageways. Those are some of the primary annoyances I see in many other games. And rolly does have some interestign gameplay and variety too. Level 4, for example throws in the new twist of mixing balloons. Level 7 lets you swim and get in a submarine. You have some choices, you can take different paths through the game. Honestly I don't think I've even seen one other game where you have real choices of playing different levels or possibly in a different order.
Now the Guildhall games are great as far as graphics (and sometimes music) goes, and they have some pretty clever moves/tricks in the gameplay, but they just don't last very long. I regret having to rate some of them so low -- I regret it because they do have some great gameplay. If they offered as much variety or length as Rolly or Ethereal Peace, then they would probably get much higher ratings (possibly higher than Rolly). But since I value the length and variety so much, and since many of the games didn't have time to fine-tune the design to work just right (there are some minor problems/annoyances left) they usually don't quite measure up to the same level.
So why is Ethereal Peace only 4 stars and Rolly 5? Ethereal Peace doesn't have any sound. That's about it.
You could ask me why the ratings are what they are all day long and I could do my best to explain... actually that might be fun to try to justify myself on every rating. But honestly, part of it is also just based on a feeling, so it might not be perfect. I have done my best to make the ratings fair, and I suspect that I could justify most of my ratings, but when you're talking about opinions, it's hard to find an absolute. If you don't like comic books or geeky kids, you probably don't like Bob the Unlikely as much. But I try to be fair in my ratings and not consider the subject matter so much as other more objective things. I generally don't like war games, but I gave TAC-B a 4 star rating because it was just so well done. But sometimes it's not possible to be entirely objective. How can one measure how good the voice-overs in "Family Reunion" are? That's probably mych more a matter of opinion.
So now you see tha challenge of expressing the ratings. I would be interested to hear how you assess the quality of a game compared to me. If I can better understand what everyone in general likes about games I can maybe rate them better. But even more valuable, if game developers better understand what people like about games, they can make better games.