Do multiplayer games on the Xbox 360 require a subscription?

I have been looking into the details of the Xbox 360 (I only own old school consoles and the Nintendo Wii) and one of the most touted features of the console is the ability to play online with friends. I was looking at the details of Xbox Live on xbox.com and it says only the Gold membership allows you to "Play games online with friends." This is appalling and goes against everything that makes PC gaming great. I don't want to start a flame war here on consoles vs. PC, but this is just crazy talk.

Is this really true? Is this enforced by all games? How much does it cost?

Yes, sadly, it's true. To play multiplayer games over the Internet, you must have a Gold subscription. it's about $40-50 / year, $20 / 3 months or $8 / month, but you can sometimes find them for cheaper.