Horror 110k, Pixel Art 234k, Adventure 208k, Puzzle 174k, Action 244k, Platformer 212k,
Horror is not the most on the platform. But horror usually dominates the popular pages, because of all the youtubers driving traffic to Itch.
What makes a game fun to play
What makes a movie fun to watch or music fun to hear? Games are interactive media, so there is another dimension to it, where the thing can be appealing. Strictly, visuals and audio are a bonus for that other dimension. There are pure text games. Games without sound. Pixel art. The most successful ever game is Minecraft. And that is as ugly as it gets in regards to high res graphics.
Mainstream games are nice to look at, because it is expected. They have the budget and no reason to create low res games. Except if they try to appeal to the pixel art fans or try to imitate Minecraft.
So, what does make a game fun to play? Depends on the genre. What makes a driving simulator game fun to play, will not be the same as will make a platformer game fun to play and differ yet again from what will make a management simulation game fun to play and differ yet again from what makes a puzzle game fun to play.
Fundamentally, you need to entertain the player. Good music and good graphics can be entertaining. There is even a /games/tag-walking-simulator genre, so some nice scenery is to be expected there as a feature. But there are just so many things that will be entertaining for different people in different ways, that there is no specific answer to your question.