Human beings have an intrinsic need for feeling valued and recognized, including you and I. This need also extends to those who are very successful, and surprisingly, even to those who are enlightened!
This means we can all touch our fellow beings by offering sincere praise and appreciation at every opportunity. In so doing we make a positive difference to others, and at the same time feel good by doing so.
The most important thing to remember is to be sincere and specific. Specific praise makes the recipient realize that you have been able to zero-in on something you genuinely liked about them and/or what they did. Providing positive, but general feedback is indeed better than no feedback or negative feedback, however, specific and targeted feedback is far more valuable.
If you are providing feedback with the mere intent of being nice, then be sure to, at the least, make the assessment honest. If you do not have trustworthy and positive observations to share, then furnishing no feedback is better than presenting an insincere one.