Well you can tell your friend that his headphones sure as hell wont make you FEEL like your in the movie. A good theater is about feeling earthquakes and explosions and having the sound envelop you. His headphones may be able to trick him into thinking its surround sound but its certainly by no means a replacement for the real thing.
Also with regards to bass, Keep in mind that with headphones the space your trying to fill is very small compared to driver size. Therefore you dont need a huge subwoofer to produce good bass in headphones.