Maybe this is just my own personal issue, but in my limited exposure to Avantasia, I find that I most often like the music more when it is a singer I am less familiar with, and I like it less when it is a singer I am more familiar with. There are exceptions to that. But I have noticed that as a general trend. For instance, I'm not all that familiar with any of the vocalists on TMOT, and I like almost every single track and easily get immersed in the album. (I mean, I know who most of them are, but they aren't from bands I actively listen to, so they often don't jump out at me). On Ghostlights, for example, on Marco's and Sharon's songs, those two VERY recognizable voices kind of take me out of the moment and have me thinking Nightwish or Within Temptation rather than being immersed in the album I am actually listening to.