No, movies use video compression to shrink the size, as well as do things like remove unneeded audio tracks. The PS2 game should fit on a standard DVD unless it's dual layer. You shouldn't or cant shrink it because of the data files that are in it. If you have the ISO, download DVD Decrypter and burn it onto quality media (Verbatim, Fuji, Rytek, Sony) at 4x and you should be fine.
Usually never, but there are a few out there. GT4, GOW come to mind immediately. You shouldn't just tell someone not to worry about it because they're usually not dual layer disks. Newer games with richer content require more space. Its become cheaper for producers to have a dual layer disk pressed than it is to produce 2 separate game DVDs like some of the RPGs out there. Until the PS3 with its Blu-Ray disks come out and get perfected, I think we're going to see a few more dual layer disks pop up.
Some of the newer games coming to the market are going to be dual layer so I agree it's best not to confuse anyone. Anyway, once you insert your game disk on your PC (and assuming you're using DVD Decrypter) you'll know whether or not the disk is a single layer disc (DVD 5) or a dual layer disk disc (DVD 9). If you use swap magic then you need to rebuild dual layer games such as GoW or GT4 in order for them to fit on a DVD 5. If you have a good chip (i.e. Matrix Infinity) then you can do a straight back up onto a dual layer disc using DVD Decrypter.
