Arifureta is pretty good, it spends quite some time before it even intimates something of a harem. Reincarnated as a slime does a bit of harem but the main character is effectively genderless (a slime) and so the harem is kinda asexual in nature. Welcome to Demon School doesn't really do much harem but isn't really a typical Isekai either. So I'm a Spider is great and the main character spends much of it's time fighting for it's life throughout the first season. Ascendance of a Bookworm is cute alternative slice of life Isekai. Knights and Magic is more a story about the main characters love affair with giant robots. Most of the female protagonist Isekai are not harem oriented (at least that I've seen, though they do have a tendency to be fanservicey for obvious reasons). Gate had it's on fan service, but was generally more serious and focused on the actual issues.
Nice, a few of those are already on my list. Slime and Spider namely, but if it wasn't already apparent I love a good isekai. Or even a bad one, for different reasons. :B
knights and magic is what would happen if magnus got isekai'ed into a world with mechs. SO MANY WAYS TO MOD!
And if I remember right when the women did do fanservicey stuff the main character was basically "why me?"
I mean there's plenty of the male harems doing the 'why me' bit, I guess they find the reluctant paramour entertaining.
Watching The Faraway Paladin, which is a variation on the "salaryman dies and gets isekai'd as a child" story. The twist is his new family are all undead. They're good and supportive people who just happen to be monsters. It's compelling enough from a character-building standpoint in the first episode, and the actual conflict of the story starts before you even realize what's going on, since his family have agendas split between their obligation to the protagonist, to their deity, and to the pact they made with the god of death.