Celtic Kings
Haemimont Games has done an admirable job of bringing together two different types of games.
1503 A.D.: The New World
While there is a lot less that's new in 1503 A.D. than you would expect in a sequel released three years after its predecessor, the core gameplay that made the original game engaging remains intact.
Port Royale
Once you get past Port Royale's steep learning curve, you may find yourself enthralled by the game's promise of profiteering and pirating on the high seas.