Forbidden Siren will require a very specific person to play it all the way and enjoy it. In my opinion I think the two sequels are better (Forbidden Siren 2 and Blood Curse), but some people prefer the first one and I can completely understand that comes down to a matter of taste.
So to somewhat trim down my thoughts, here's things I can mention about the game:
-The enemies are creepy, the Shibito as they're called are very creative twists on just a typical zombie that manage to retain a level of creepiness through the whole game.
-The setting is fantastic, the rural Japanese village with all sorts of shanty towns and ritualistic sites is a good one.
-The music is original, fitting, and some of it even memorable in a very unorthodox way.
-The story is initially confusing and when you first beat it you may not 100% get everything, but there's a lot of small things to pick up on and a few things you may realize or notice that can completely change your outlook on certain aspects of the narrative.
...So let me get this all out of the way. All of the above I think is fantastic. So what issues do I have with it that makes me prefer the sequels to it?
It's fucking pacing and the format you play it.
In Forbidden Siren, the original, the game is set into different stages. For the start of the game you go between these stages in a linear fashion, until you break a 'loop', and then you get a stage select as you unlock more stages on this table graph which represents which character you play as and at what time along the timeline the stage occurs. In Forbidden Siren, there is a big theme of 'time loops', you need to change things to break out of a 'loop'. And what this translates into in gameplaty is replaying the same stages over and over again.
Siren at its core is a game about figuring out what the game wants you to do, then executing it well, and figuring out hidden objectives to do alternative things in stages. Each stage has two objectives and then possible one or a few hidden objectives. The only way to really progress in Siren is to begin to figure out how the game works, to both figure out how to deal with certain scenarios, enemies, situations, and pick up on the clues (sometimes cryptic as hell) for what to do in order to get a different outcome. That and figuring out which stage you need to go to in order to make this change, often doing a mission in one level will change something in another level as sort of a chain of levels you need to replay in order to make a change in a much later level so you can complete a hidden objective.
There is fun to this, I don't regret playing it, but this is up there as one of the longest and most demanding horror games. It sometimes is difficult, to the point of being cheap, and it's kind of hard to progress far until the logic of the game begins to click in you and you begin learning the sort of beats the game usually does for hidden things (though a few are still way out there). But I personally think because of how thoroughly you have to learn this game inside and out, the horror aspect is kind of front-loaded as there is basically no unknown to the gameplay as you get further along in the game as you literally have to figure out how everything works to progress.
It's enjoyable and unorthodox and some love how it's a lengthy kind of logic puzzle in a horror game with all of its challenges, but while I did enjoy it well enough I do think after my last playthrough where I near 100% the game I never want to play it again. Like literally expect to spend 40-80 hours to beat it. Also the game has a fakeout ending that's one of the loops and doesn't unlock multiple stages, missions, the final boss, the actual ending, etc., but you need to see this ending to break a loop so know that.
As a result, I find the game hard to recommend except for some specific types of gamers. I will say this though, there's hardly anything else like the Siren series or siren 1, all three Siren games have things in common but also drastic differences but all three are very unique.