There is nothing Biblical that says (as far as I can remember) that non-Christians are incapable of being good. Nor does the Bible teach (according to what I've studied) that non-Christians are incapable or suffer from a diminished ability to experience and display emotion.
The difference is the source of the aforementioned good/emotion. From my past experience (having spent several years as a non-Believer), I can say that how I feel emotion and how I regard myself as "good" is completely different since I've returned to my walk with God.
Trying to define myself as "good" from my worldy perspective, or more appropriately, as I look back at how I was trying to do good from a non-Christian standpoint, I can see that my efforts were seriously lacking. I might have been "good", but the satisfaction was only to please myself, and ultimately lacking. After having returned in my walk with God, I don't worry about trying to please myself by doing good, I do what I can to please God. And HE lets me know that my efforts to "do good" have paid off.
As for displaying emotion (capacity to love, feel empathy, sympathy, emotion in general), again, there's nothing to say a non-Christian can't do these, but there is a supernatural capacity I think Christians experience. I don't mean X-Men type supernatural capacity, but a spiritual capacity that simply defines a Christian's capacity differently than a non-Christians.
Paeter, I'll defer to you to correct the following (as I know you are more learned on this than I), but the Greek (?) defines love in 4 way stages/terms;
philia, which is a friendship or affectionate love; storage, which is family love, such as a parent for a child; eros, meaning a passionate love, with sensual desire and longing; and agape, which means an unconditional love. This final love, agape, is the kind of love that God displays for us. As sinners, we don't deserve anything but death and separation from God for eternity. But because of his agape love for us, God sent his Son to be our saviour.
It's this type of love that we as Christians work so hard to emulate to the rest of the world. Our relationship with God is what helps us learn and understand that agape love. If a non-Christian has never experienced, or understood, or even rejected, that agape love, then how could they express it to someone else.
This is why I say that non-Christians aren't diminished in their capacity to love, they just can't express it on the same level or in the same terms as a Christian. It's a different type of love.
That's just my humble interpretation of the question. Won't say it's right or wrong, just my current understanding.
May the Lord of the Force be with you.