Roseann,
Great question. Most Disney enthusiasts would say that regardless of age, there is no better park than the Magic Kingdom. But I find most older teens seem to be more content at either Epcot or Hollywood Studios.
Epcot goes over well with teens that like to interact with other youth from around the world. With all 11 national pavilions staffed by young adults from the host countries, there is a lot of that going on. If your teen likes to do a bit of shopping, it is not bad here either. Epcot also offers a couple of true thrill rides.
But probably the best bet for a teen boy is Hollywood Studios. The thrill rides are great (
The Twilight Zone Tower of Terror,
Rock 'n' Roller Coaster Starring Aerosmith), and there are shows that might be a bit more his style (like
Lights, Motors, Action! Extreme Stunt Show, and
Indiana Jones Epic Stunt Spectacular!). There are more things to do there that he will probably enjoy, both the kind that let him be a kid again, and others that are a bit more mature.
I am glad to answer any follow-up questions you may have!
Have a magical experience!