it all comes down to specificity really, you need to anaylse how you train and why you train, If you have been essentially performing bodybuilding type routines with high volume medium intensity etc then the gains you accomplish are not going to be conducive to sports performance, its been said that bodybuilding is essentially endurance training, at a high relative intensity.
so if youve been following high volume bodybuilder type routines muscle growth you have achieved may be sarcoplasmic hypertophy, which is the growth of the cellular space, this type of growth is evidenced in bodybuilders, is charctersied by a decrease in muscle density and little corresponding increase in strength, compared to sacromere hypertrophy wherein the contractile elements of the muscle increase in size and number which increases the area density and has a greater ability to exert force.
There a so many factors that could present here for your lack of relative (hate that term!!) strength. As has been mentioned, your lack of strength could be neurological reasons (poor intra and intermuscular coordination) poor motor learning, the list goes on and on...
strength is an enormousley complicated motor ability, however all strength types are mediated centrally, the nervous system is ultimatley respsonsible for any strength activity.
This basically tells me your training is off, yes people respond differently, the principle of individuality states this.
The body is essentially like a piece of clay, you can mould it to pretty much achieve anything you want given the right stimulus (training), the central nervous system moulds this clay, training provides the tools!!
So, if I were you post your current training program, numbers etc and any other info you feel relevant, like typical diet, sleep patterns etc etc That way people have more information to work with and may be able to help you out more.