Actually it was a pretty awesome game, despite having different controls from every other RTS; the focus was more on trade than military which was pretty cool. They ended up making a few higher budget sequels as well: https://en.wikipedia.org/wiki/Anno_(series)
Unknown Horizons is basically a clone of the original Anno 1602, and I've been sort of following the development for 6 or 7 years, always thinking "that would be the perfect open source project for me to contribute to" but sadly I haven't really spent much time playing it and haven't written any code for it.