http://en.wikipedia.org/wiki/Anno_2070
http://anno-game.ubi.com/anno-2070/en-GB/the-game/index.aspx
Anno is the best and best-looking city-building/economic franchise that currently exists (and it's not an RTS franchise even though English speaking websites and reviewers always claim that; it just has RTS elements). Anno 2070 is the latest entry and a great game, the best franchise entry - each Anno PC game is a million seller - though is Anno 1404 due to the great setting imo, I just recommended Anno 2070 because it's great game as well and available on Steam.
Info about Anno 1404 and its add-on Venice: http://dawnofdiscoverygame.us.ubi.com/pc/ (US name: Dawn of Discovery, original name: Anno 1404). Anno 1404 is not available on Steam anymore unfortunately (and fans are begging to get it back on Steam: http://steamcommunity.com/app/33250, scroll down to see some stunning screenshots, this game is from 2009 btw), but it can still be bought retail or digitally, e.g. on http://tinyurl.com/mhotad5 , http://www.getgamesgo.com/product/anno-1404-gold or on Ubisoft's own site. Others may disagree with me, but imo the two latest Anno games on PC (1404 and 2070) are far more recommendable to SimCity fans than Tropico or Cities XL.

You forgot the best part, all games on GOG are DRM-free.

If you like CoH I would recommend trying out men of war series too, they're quite similar

Fallout 1 & 2 = hold out for wasteland 2

Europa universalis IV if you really love grand strategy with empire building and dont mind spending hours upon hours learning to play it, dont get Rome 2 total war yet, they essentially sell you a beta for 60$.

To test your PC's prowess, I'd recommend buying the original 2007 Crysis. It's also a very good game, so if you haven't played it already, give it a try.

Depends what you've already played on consoles:

Exclusive:
Hard Reset
Mount & Blade
FTL: Faster than Light
Total War
Amnesia: The Dark Descent
Darwinia
EYE: Divine Cybermancy
Civ V (get it with the expansions when you get it; they really add to the game)

Multiplats worth purchasing and modding beyond recognition:
Skyrim
Fallout 3
Oblivion
Crysis
GTAIV

Yea, I might just do that. Bought Starcraft II today, I'll hold out for Anno and SimCity (Origins)

I have it for 360, and I'm halfway done. I don't want to start all over again lol.

Witcher II and Starcraft II are apparently card pushing games and from what I read online I can play them on Medium-High.

BTW I have a 650TI graphics card.

Mount & Blade (Warband is probably the best bet)

Chivalry

The Witcher (Witcher 1 is good but long and has some slow sections that drag on so you can skip to 2 if you really want)

Recettear: An Item Shop's Tale/Fortune Summoners

The Binding of Isaac

Dungeons of Dredmor

Avernum: Escape From the Pit or alternatively Avadon (both are good entry points into Spiderweb software's RPGs)

Dawn of War 2

Orcs Must Die! 1 & 2

Crusader Kings 2

S.T.A.L.K.E.R. (make sure to grab some mods, Complete mods are pretty good at fixing bugs and balance without changing the experiance too much)

Check out these sites to find good deals on games

http://www.deals4downloads.com

http://www.greenmangaming.com/

Green man gaming has Civ V plus the two expansion packs and a bunch of DLC for $27.19 (and use GMG20-8MUTY-M21VN to get 20% off)

http://www.greenmangaming.com/s/nz/en/pc/games/strategy/civilization-pack/

It's a steamworks title so you will get a steam code, so no need to wait buy it NOW! lol

You gotta pick up Counter Strike Global Offensive and play with me :D

Just wait for the Steam sales, you'll buy more games you need.