I like both fantasy and scifi. I like these genres in books, films, TV shows so I almost always include something fantasy or scifi to spice up my game.
I would love to have magic or to be able to travel to another planet myself. Of course I can't do that in real life so I enjoy it if my sims can.
I do appreciate realistic packs as well. For example I like sending sims to university, 'normal' sims and supernaturals alike. And my mermaid with her half alien daughter still has to do laundry. Realistic packs can add a nice touch to my supernatural sims lives. As long as I don't have to play 100% realistic I am happy.