In some cases, yes, 'You're too good for me" is just a lame excuse to cover up the fact that he wants to go date other people, he's just too ashamed to admit it and doesn't want to hurt your feelings. In other cases, some men really do feel like they are unworthy of being in a good relationship. They have very poor self confidence and convince themselves that they don't deserve love or friendship. Some people, who are serial cheaters, tend to break it off with someone that they really like because they don't want to hurt them by cheating.
Without much background, it's hard to hazard a judgment either way here. Just think about how well you know this guy and how his past relationships ended. If he has a history of infidelity, he may have broken up with you to avoid hurting you.
The worst thing about these types of break-ups are the lack of closure for the person being told that they're "too good" because it's really not an explanation, it's an excuse. If you really need some closure, then confront him, if you can. Tell him that you aren't trying to stir up trouble, you just need to find out what the truth is behind the break up. Tell him that you aren't there to get mad, you just want some closure so you can move on.
If he won't talk to you, there isn't much you can do beyond that, but let go of the past to make way for the future.