Honors lists, such as magna cum laude, are made public at the time of graduation, as are the graduation list itself. Obama does not claim this, it is a matter of public record that he graduated magna cum laude(with great honor) from Harvard Law School.
trump did claim he got an MBA at the top of his class. It is public that he never got an MBA from any known school, and he never graduated at the top of his class. "Top of the class" really isn't a thing at Ivy League graduate schools. I don't know why he thought he could get away with that.
Then those claiming it should provide proof of their claim. Their claim is meaningless without something to back it up.