I think that this project / thread will be much more successful if a real budget was in place. The responses one should expect from build suggests are ones that maximizes performance given the allotted budget.
Right now, the discussion is focused on how cheap you can build a computer that can run the games you specified on max (it seems that the future proof requirement has all been dropped, and in reality, not a very sustainable concept on a budget build), which is exactly what you said in one of your followup responses. My concern about this approach is that if you aim for 'just right', you run the risk of being short (for example, someone may recommend a 'just right build' that works well in their experience, but your definition of well may be 60FPS while the ones providing the recommendation's definition is 30FPS). A build may run awesome on 720p, but not so much when upgrading to 1080p. Games may receive content/expansion or graphics updates (like Skyrim's official HD patch) which will increase the demand of system resources.
Just remember that we don't take any responsibility for suggesting an inadequate build ~ you're the one who has to pay and live with the system.
If you build the best computer you can willing afford, you will not have any regrets if you run into the issues I stated above, or when you want to play a more graphically intensive game.
Meanwhile, you should define your needs more specifically, such as desired size limit (there can be huge differences between MicroATX, Mini-ITX, and standard ATX - I built a MicroATX and was quite shocked at how big the case was in person. I am building a MiniITX atm), weight, desired FPS in said games or the resolution you intend on using primarily.
Another disclaimer is that from my observations, not everyone defines 'max' the same. Max is every setting on the highest quality possible, but some deviate by having most on highest - but as a quick example, turn off shadows.
Edited by minnus - 4/25/12 at 10:28am