Of course you can try to make him feel better, but I wouldn't bring it up unless he does first. When he does, the best thing you can do is listen more than talk. Some of us think we have to give advice and solve the problem (I'm bad about this--it's the dad in me) but really, people just want a sympathetic ear and a supportive shoulder. There's usually not much we can say to help them, anyway, except for the same old tired platitudes: "It will all work out." "You'll get into college somewhere." "It happens to everybody." Those things might be true, but they don't help much when someone is freshly wounded and unable to see past the dark clouds surrounding him.
In your guy's case, rejection is a part of life that we all have to experience--it's how we learn and grow and build character. What he's going through today and how he learns to cope with it will help him a few years from now when he doesn't get the job he wanted or the woman he asked to marry or the seat he wanted on the board. Life is full of rejection and disappointment; it hurts, but it makes us stronger. Good thing, too, because believe me when I tell you that the older you get, the more intense and life-affecting rejection can be. But, you can handle it better because by then you've had lots of practice.
So let your guy experience what he needs to experience, listen to him vent and sympathize with his pain. If he asks you questions or wants advice, sure, you can try to help, but the most important thing you can do is simply to be there for him. Oh--and take him bowling. Bowling always helps me. Distraction is good. Distraction and nachos. Bad nachos--but bad in a good way because they use that fake gooey cheese product that's mostly butter but by god it sure is tasty.
Thanks for the question.
Simply be there for him--yes. You can't change the fact that he was rejected, but you can offer your sympathy and support. Good advice.
Oh, and nachos. Yes, those are good too--ha ha! :-D