friends grow apart unfortunately, it happens as people begin to age and develop their personalities, they begin having different tastes, interests, hobbies, etc..
Just leave the guy alone entirely.. If it truly is a good friendship, he will eventually call you up and say "Hey man, haven't heard from you in months, whats new with you dude?".
just ignore him entirely, if he still wishes to be your good friend, he will make the first move..