Nutaku is probably the biggest name in the business of Hentai games. The site sees a staggering 100,000,000 visits each month. That alone speaks volumes. But you need only feast your eyes on the site itself to see that this is a high quality developer. The site is beautifully designed and easy to navigate. This is already a far sight better than most porn games that don't even have websites and simply advertise on porn sites.
Generally speaking, the world of porn games is pretty shady. Most games are from mysterious developers, and almost impossible to find clear information about. And don't even get me started on the shady marketing tactics. 9/10 games will show you footage that's not even from the game just to get you to sign up. And the "we need your credit card info just to verify your age" baloney is ubiquitous in this space.
In light of all this, Nutaku is a breath of fresh air. Not only are they perfectly transparent with pricing and information, but each game on their site has its own info page with descriptions, features, game details, prices, and even pics and footage from the actual game. You'll know exactly what you're buying, with no monetary leap of faith or credit card details required.
Nutaku offers a wide array of games across all genres. They offer games from large established developers and small independent game designers alike. They offer both free and paid games. There are games for different tastes, fetishes, orientations, and gaming preferences.
This mountain of games is extremely well organized and searchable on the site. The intuitive interface and sophisticated search and browsing options make honing in your ideal game extremely straightforward. And if you don't know what you're looking for, you can always browse by popularity, type, cost, etc...
The quality of the games they offer is top-tier. Only a couple of other sites come anywhere close to competing. And even still, the wide selection of games alone probably solidifies this Nutaku's title as the King of Hentai Games. And in The Porn Genie's humble opinion, Nutaku is #1.