You’ve tried two drives and the result is the same?
Is your 2nd drive bay empty? Did you try the drive(s) in the 2nd bay using the alternative cabling/connectors?
If you do have a disc in the drive that won’t eject via keyboard, will it eject if you drag its icon to the trash?
When discs won’t eject, can you still read the data on them? Are they usable otherwise?
If you select FORCE QUIT from the apple menu, what applications does it list? Maybe you have something that is locking up the drive resource. When I have Toast open for DVD burning, it overrides normal access to the drive. Maybe a virus scanner is reading the drive?
I’m not sure if the power settings affect the superdrives or not. In System Preferences, look at your Energy Saver settings. There’s an option to “put the hard disk(s) to sleep when possible”. When drives are idle, the computer puts them to sleep. If this is checked, try unchecking it.