Anno 1404 is a visually spectacular city-building game with multiple levels of resource management and solid game mechanics.
While the DRM in retail Anno1404 is still a put-off, both 1404 and its sequel: Venice offer a wonderfully slower paced goal-oriented and occasionally hectic game. (Yes, there are RT battles!)
I have no experience with the on-line version, but treat it like a demo to see if you might like the game. I'm sure you can find Dawn of Discovery Gold (both games) for short money somewhere for DL or traditional retail box.