I'm just not into ghosts and supernatural stuff, if I can't relate to the characters in some kind of way then I cannot immerse myself into the story or care about it (I can make some exception) and ghosts are something that I despise almost as much as girl with wings or magic powers and I cannot relate to the characters for various reasons that are way too boring to explain right now and are not relevant either, btw my comment was almost a complain to myself and my tastes rather than a critique to the genre itself or visual novels that revolve around this theme in particular.
Slice of life can be amazing, though like you said it requieres good writing skills, a good setting and for the writer to think outside the bounds of what is pre-established, like school life, eating, food talking and repeat... is like most of the writers cannot conceive anything else than that, you can have some amazing slice of life without romance at all too, then again you need some good sad drama to go along with the slice of life, for example the diary of aya kitou is pure slice of life (if your turn it into a vn it would be a 100% utsuge ) and if you can't go for slice of life alone then I would prefer sci-fi rather than magic or supernatural stuff but this again is just a personal preference.