I don't think internet is required to install/play the game, I did not need it. Why would internet be required if you're getting the game on a disc?
You don't need internet for the pirated version. That works. Oh please don't arrest me or go all bitch about it because I mentioned that.
Kill it with fire! Kidding. I have a couple of PS3 games that i'm planning on selling-since i don't have PS3 anymore i don't need them.And i'm thinking of picking up three or four copies of Metro 2033 for those of you that don't own it. But we'll see.
Any steam game requires that you are connected to the internet to finsih installing the game, and steam is always releases new patches so you need internet to get them.