Depends on the graphics. If an image is already at a high resolution, then there wont be any quality degradation when displayed on the iPad. Same goes for vector graphics, if any. For the rest, itll look blurry; as an approximation, just take any image and zoom in to double the size. So in conclusion, if a game has a mixture of all 3 types of graphics above, the result will be quite nauseating lol
Well from what I gathered from the announcement, the games will generally look a little bit worse, but not much. Of course, if the game is designed with the iPad in mind, or for the iPad itself, then it's all good.
From what I've read the iPad does do some anti-aliasing to the game, so that'll help. It'd be like playing a PS1 title on the PS2 with the graphical smoothing option enabled. On the other hand it would be fairly easy for the dev to simply let Open GL do the upscaling, which would likely look much better.
My father was showing me some pretty cool stuff with graphics these days. Now he's the computer expert but he showing me simple image that he had coded and he was able to increase and decrease the size of the image with hardly any resolution loss. So you can have one image file for an image instead of having multiple files of the image in different sizes. From what I've tried to figure out I think this is how the coding works for iPhone apps
Here's where texture filters might come handy. However, most iPhone games probably don't use textures with a higher resolution than needed for the HVGA resolution (320 x 480). Therefore I expect that most native iPhone games will loose a bit in quality when run on an iPad without modifications - whether there's antialiasing anabled or not. Btw, can't wait to get my iPad.