I'm pretty sure there are a bad bunch of discs that are readable on some drives, but not all.
I bought a copy of BF4 and immediately had a problem loading disc 2. I haven't had a disc problem with any other games so I exchanged it for a new one thinking I just got a defective game. I had the exact same problem with the second game so I started searching for a solution. I tried all the suggestions in this thread (deleting cache, re-formatting the HD, etc.), but nothing worked. I presumed it was a problem with the DVD drive on the Xbox.
I've got two Xbox consoles - an old one with a 60GB HD and a slim with no HD. I was able to install the disc 2 to a USB flash drive without any errors. I thought I could then just transfer it to my older Xbox with the HD, but no such luck - it wouldn't allow me to transfer it. My next step was to remove my HD and connect it to a friend's Xbox and install it from his. That worked, but as soon as I tried playing the campaign version from disc 2 I almost immediately got the disc unreadable error.
I figured at this point I had little choice but to replace my old Xbox or buy a HD for the newer one. Just for the heck of it, I tried exchanging the game one more time and the third one worked perfectly. I was able to load the disc onto the HD and play the game without issues. Out of three games, I got two defective ones and one good one.
Ok EA - your turn to address this situation. You obviously have a bunch of games out there with marginal discs. Fix it please!