You have to realize we all listen for different purposes, this is more an audio physiological case where your friend obviously has a crush on hearing and feeling as much bass as possible while the rest for him is ok if it's "just there". He gets the enjoyment out of hearing & feeling this "wubwubwub" sound, not to hear all the fine details in music.
Different strokes for different folks, that's why he continues to persist the Skullcrushers are the best, you could let him audition for example Sony XB500, it might be a candidate he might like more but the skullcrushers still have this built-in vibrator though which tricks people that it has godlike amount of bass while it actually hasn't it's just a very ridiculous midbass spike with very lacking subbass frequencies. XB500 again would output more audible bass but due to lack of built in vibrator he might still prefer Skullcrushers but XB500 do output so strong bass pressure you so can even feel it. So yea, let him try a XB500.
The best cure for this kind of cases is giving him MORE of what he wants until he eventually gets bored out of it.
Edited by RPGWiZaRD - 12/12/12 at 1:01am