With regards to games: Simulators like Transport Tycoon, Railroad Tycoon, and similar games had decent popularity among people I know, but their sales were not nearly as strong as RTS or FPS games. The market is there, but going after it will be taking a slice out of a probably smaller pie than other markets. However, you'll also have less competition over the size of the pie, which can translate to being far easier to stand out from the crowd in with a really solid, well thought out, and highly polished title.
My take as well.
The games exist and there is a market for them. People play them. There are potential customers.
The number of potential players is still huge -- millions -- but not as huge as the markets with tens of millions.
I enjoy economy-based games. It ranges from games like Railroad Tycoon and other build-and-expand games, and I've enjoyed quite a few settlement-style games where you start by building a woodcutter, lumbermill, then a smelter, toolmaker, and mine, working your way up to full expansive economies.
Unfortunately the biggest vocal people in the video game industry tend to dislike economic games, it is common to hear them misinterpreted as RTS games. Economics is about gradual building, about exploring the interplay between social forces, where many people seem to prefer jumping straight to the army and the epic battles, forgetting about all the critical steps building up to the battles, the economic paths of building the weapons and armor, recruiting the soldiers, keeping the army fed, building and managing supply lines.
I enjoyed BlueByte's series The Settlers, with #4 have a fun oddity where the game is best won by manufacturing the most shovels as rapidly as you can, along with just enough military to defend the shovel-bearers, rather than more typical military-style combat. I remember at the time reviewers talking about how they just abandoned the economic approach of building gardners to take over, instead sending hoards through the swamps and hoping enough military survived to win rather than gardening their way through the swamps as it was clearly designed. Reviewers consistently pan the series for a slow pace and not enough combat, reviewing them in terms of RTS and not in terms of economics, so it is clear that mainstream perception in the US among reviewers is fairly poor.