"Run everything out there" is a really open ended criteria.
If you're planning on playing with a WQXGA display or have a 3 way 1920x1080 display set up (why not go nuts with a 3xWQXGA and be the only kid on your block) and you're planning on playing in 3D, the "run everything out there" requirement skyrockets from a basic 1920x1080 single display non-stereoscopic signal.
Reality is, top end VGA card set ups (3x top tier VGA cards) are really only required for those 3 way display set ups and other extra high res output modes.
RAM requirements really haven't changed much; people configure PCs with more memory almost because memory has become so cheap, but even 8GB for gaming covers everything. I'd argue even 4GB covers any current game regardless of hardware overhead, not that anyone should do a new build with so little memory as you'd save next to nothing.
There are a lot of benefits to be milked from the use of SATA3 SSDs, but even with the per GB premium dropping fast, very few will spend the premium to install all their games on SSD. But at minimum, SSD boot drive for OS and most frequently used apps/games.
CPU wise, any of the quad core hyperthreaded Ivy Bridge chips would do. Any self builder is likely to be an overclocker, so K version only. For a new build, there's no need to use older parts.
As for how long it will last, if you spend over $2,000 on a self build, you'd probably be fine for the next 4 years even though you'd lose your e-peen bragging rights within 1-2 years and might not be running those hypothetical 4 year in the future games at max quality/max res at 60+ fps.
It all really boils down to how much you want to spend on an annual basis to keep current.
In most cases, a builder is better off doing a fresh mid/high grade build every 2 years (between $1,000-1,500), recycling the few parts that are salvageable (drives, PSU, case, etc.). Really, all you're replacing is MoBo, CPU, RAM, and VGA cards. Of course that's about 80% of a new PC.







