If you think my PC is good, then you should see some of the true gamers' machines out there... some of them literally cost thousands of pounds to build
Mine does judder a bit here and there when playing some games at full detail. It's nothing I can't live with, but I know fine that the next Elder Scrolls game will need a system a bit beefier to run at max settings (which is something I aspire to do; the game looks STUNNING).
Besides, my stepson also wants to be able to play the game; his current rig has no chance (it's one of the first-generation Core2 Duo chips, 2 GB RAM, and an old nVidia GeForce 7200 card). He'll be getting my old mobo/CPU/RAM, which should be enough to play the game reasonably well.
Games are just getting bigger and bigger, due to the increased detail levels, and larger higher-quality textures. Therefore, you need need more and more memory, and the faster your PC can access that memory, the better.
My own PC runs with DDR2 memory, for example; I think I'd benefit from getting DDR3 memory (higher memory access speeds, necessary for transferring larger textures between the processor and memory) and the higher front-side bus speeds associated with the newer Intel processors (I think the Core i5 is the one I'd look at getting, if the Core i7 is still stupidly expensive come August time).