You want to know what is in part making you guys seem so disappointed about the voice actors?
It's because they forgot to do something. They seriously took this half assed. It's subtle, but there, and more noticeable at some parts.
Guess what? You know how the KH series has done a great job matching mouth movement with the actual dialogue, even in English? Well, they didn't do it in Re:CoM. Yup. They just took the Japanese footage and basically did the English dub directly over those cutscenes, not even bothering to change mouth movement.
How'd I figure this out? I had a bad impression watching the video on YouTube, I knew something wasn't right. And then I paid attention to Sora's lips and saw that they move in the exact same manner as they would if he were speaking the Japanese dialogue. So some of the dialogue sub-consciously gives the impression of being unnatural. In fact, I imagine they had a bitch of a time trying to conform their words to the Japanese mouth movement as best they could. That would thus force, in some respects, the voice actors to not be... very good.
Don't believe me? Check the part where Sora says, "What's this, a card?" Watch closely. Notice how his lips don't match his mouth. Then check that same part of the scene in Japanese, keep the dialogue in mind, and note that the lip movement matches up perfectly.
I can't believe they neglected to do that. Very, very shameful. Like they didn't even care.