Some animes harem or not involve a person dying but being reincarnated into another world, either with a new body or the same one. The world they're reincarnated in is usually a magical one, but the protagonist reincarnated is granted magical powers by God or other deity's.

Imagine Spike was in an accident but was reincarnated into a magical like world with certain magical powers that make him adored and feared. He makes a new living for himself while at the same time attracting the hearts of several girls.

Some anime examples include

In another world with my smartphone

The Rising of the Shield Hero

Wise Man's Grandchild

By grace of the gods

That would sound great!

It all depends on how it's executed, honestly. Sure, the premise of going to a fantasy/game world after getting summoned/reincarnated is neat and all, but sometimes it's not that great if the characters are bland and the plot's not good.
Using Rising of the Shield Hero as an example (I've read all the light novels, for reference), while the power aspect is interesting up until Naofumi's so ludicrously overpowered that he can deflect concepts, the characters are trash. The only redeemable ones out of he lot are Naofumi and Raphtalia, while everyone else is either cartoonishly incompetent, or enables Naofumi's worst tendencies. It obviously tries to be a subversion of Isekai tropes, but in the process, the motivations of the characters are so paper-thin (which the anime conveniently leaves out so that there's even less nuance than before) that the main antagonist of the series is less developed than Kayaba from Sword Art Online.

My thoughts on an anime aside, the success of an isekai is bound to its premise and its execution. What are the circumstances that the protagonist arrives in another world, and how does that affect the plot and themes of the Isekai (Did they die saving someone's life, were they a NEET looking for validation, do they jump between the main world and the other world, are they a hero or a villain, is this their first time in a world, is it their first time in that specific world?)? What questions are asked when placed inside of this world? What are said world's standards? Will the protagonist abide by them to survive, or change them to suit their benefit? What power does the protagonist have, and how creative will they be with said power moving forward? What sort of dynamic do the characters have with the protagonist, and how will they contribute towards the plot; giving the reader a reason to care about what happens to the world, directly aiding the protagonist in battle as compatriots? The list goes on.