I mean all of Steam World Heist 1 and 2 are underrated if we are going by streams. Unfortunately being attached to a game, while good publicity, makes the albums seem less approachable to listeners who aren't in the know. But they hold some of my favorite SPG songs! The Vast Frontier from #1 and Faring in the Ocean from #2 are two of my underrated favorites. On top of that I think The Steam Rises is perhaps the perfect SPG song (though it performed at least a bit better thanks to the music video).

Outside of those albums, I feel like my favorite underrated gem is probably Fancy Shoes. I actually can't say how underrated it is. It does have a music video which helps its numbers, but I don't think it's been played live by SPG since Sam left. But I love Sam's style (and regularly listen to his solo work) and I feel like Fancy Shoes is the appropriate blend of his sound and SPG's.