Depends on what you like, as flavors matter a lot.
Being a DIK is probably one of the best out there. It's been around for a while so book one (CH's 1-4) is a bit dated, but it gets better. Theyr'e on patreon wrapping up chapter eleven, and they release books every four chapters on steam, gog, and maybe itch? Not harem, VERY replayable for different paths of love interests AND different paths of personality. There are mini-games which you can turn off (I prefer them off, but I have one play through that I have them on for).
A lot of people love leap of faith (warning topics of suicide). It's not harem based and some of the love interests really require a guide to achieve. A lot like the Cece path, and I think that's doable without a guide. I did a lesbian threesome path and I hated it and that colored my impression of the entire game. Completed story.
Chasing Sunsets - Not harem but instead two love interests and the ability to F around with others. A threesome path is possible but the criteria requires more than casual play and probably a guide? I had to look up what I needed to do to achieve it. I'd say that you just want to make save and max points, but maybe do that on a follow up play through because a game should be fun. Completed except for CH10, a prologue. Will be completed in 2025 and pretty good.
Love and Second Base is a HUGE dating simulator with a lot of grind, but also story and the amount of game/content you get WAY exceeds the cost as long as some grind for money/other things is okay with you. It can be harem but with boobie traps everywhere if you don't know the game or use a guide, but a first playthrough should be done for fun and then a second to get more stuff ( you carry over stats so it gets a bit easier too).
Ripples is awesome.
Become a Rockstar is fun.
Come Home has a lot of diversity (and maybe not the best looking models), but more realistic women personality as it's written by a woman and it shows as opposed to be a virgin's lust fantasy which a lot of the AVN's come across to me.
The deluca Family is a mobster based good time. Book one is complete but the story is ongoing. I was caught off guard by how much I liked this one.
Good girl gone bad is a great corruption game (female MC that gets corrupted based on choices the player makes).
Sisterly lust had great writing, but is a family game. I'm not a fan but it's frustratingly hard to avoid with adult novels. I thought it was good and would recommend if family love isn't an issue. I believe it can be harem or single. Different paths and choices matter.
If you like dark games/tentacles/monsters/demons/goblins/whatever, I'd recommend ravager (2025 completion), parasite black (who knows when complete), and seeds of chaos (who knows when complete and I think patreon was messing with them about content).
Desert Stalker is one of my favorites. Not complete but a lot of content. Think madmax and know that you can slit a throat and face bang a female you defeat in the first five minutes. The tone doesn't have to be THAT bad based on choices you make, but it IS a dark world and those five minutes certainly set a tone and expectations. Note that the darkness I mentioned is the PLAYERS choice. For the most part I thought the game did a great job on giving the player autonomy about the flavors they wanted. Also, one of the best wifes I've ever run across as they remind me of mine and reflect a healthy relationship that is fundamental to real life harem/multiple other parties in a relationship. So best wife/harem #1 in all VN's I've read.
Actual Roommate is a great lesbian game with a VERY cute MC. I loved the writing and humor but humor is subjective. Also, some people may not like lesbian games.
I could name more, but that's a lot.