I saw a thread for this, but it was made way back in 2015, so I thought there’d be no harm if I made another one. “Underrated” doesn’t necessarily mean it didn’t sell well; perhaps it did, but it didn’t get the attention you believed it deserved here on the forums. The title says “COG games” for simplicity, but it could also include complete Hosted Games and WIPs.
Off the top of my head, A Crack in the Spyglass is massively underrated here. Well-written, interesting concept, entertaining even if the demo is short, and yet it hasn’t tracked much attention. Betovering House is another one (it inspired me a lot when writing my own WIP) that should have more fans. A more recent one that I really enjoyed was Whisper in the Dark.
As to COG games, I have no idea whether it was successful or not, but I didn’t see many people talking about Blood Money by @HannahPS here on the forums, which is a shame. I was very happy that Crème da la Crème was popular here, but Blood Money is just as good. As soon as I played it, I became a fan and consumed any work of hers I could find!
I’m well aware that all out of the three WIPs I listed, two are on early stages and one hasn’t been updated since March (unfortunately), which is a big reason as to why they’re not all that popular yet. But I’m still hoping this could turn into an interesting conversation and bring attention to more underrated games.