There is no such an industrial standard for RAW format yet, every company has their own interpretation of RAW in their dSLR cameras. You have to use the software they supplied with the camera to open the RAW files.
PhotoShop's RAW plug-in is compatible with many major camera companies' RAW format because of the high demand of using RAW in Photoshop. iPhoto is considered consumer product, its unlikely Apple will work with every single company to make iPhoto compatible with their RAW formats, it only compatible with few.
The advantages of using RAW is not on the resolution, its the ability to tweak the image a lot more than fixed TIFF or JPEG (of course JPEG is also loss format because of its compression). A camera raw image file contains the unprocessed data from the image sensor of a digital camera.
Just a side note, iPhoto doesn't really support RAW image by definition, you can't work with RAW directly, what it does is convert compatible RAW images to JPEG in iPhoto.