Firaxis made a Colonization stand-alone "expansion" using Civ IV's engine. Alpha Centauri could REALLY use the update as well. It was the only Civ-like game I actually liked. I've seen some mods for Civ IV for it, but I'd rather that Firaxis give it the full treatment.
The Star Control series, especially Star Control 2 were really deep expansive games with a lot of backstory for just about everything. I officially ignore Star Control 3 as it is utter garbage; the developers know nothing of the Star Control universe, and tacked on all this contrived junk and retcons.
Transport Tycoon was a really fun game, and one of the older "Tycoon" games before they became a genre. I ignore Locomotion, as it is Rollercoaster Tycoon without rollercoasters. Track by painful track layouts, especially on straight runs was just about ready to give me carpal tunnel. Dragging and dropping straight track would be best, really.
Katamari Damacy + realistic looking models = absurd hilarity. 'Nuf said.
Sim City with even more realistic layouts. Many metropolitan cities don't have perfect grids as roads are concerned, as some are angled, or curved, or staggered. An intelligent way to design such roads as to have a miniature Chicago, New York City, Los Angeles or Dallas would really be nice.
Asheron's Call was the second MMO that I tried and I stuck with it. It had a really rich character system which was sadly dumbed down in Asheron's Call 2. What my friends and I find really good about Asheron's Call is that it is not gear centric; it's entirely based on skills. In my opinion that makes for a better game than to turn level 5, get all the obscenely overpowered gear and then become the equivalent of a level 30. Equip two people with the same weapons and armor, and one will have a huge advantage over the other in knowledge and skill if the other is a total novice with the equipment.