Well, the solution to your problem depends on the game you examine - as different gaming mythologies handle encumbrance in drastically diverging manners. For example, it is often accepted that Dr. Gordan Freeman's mechanized exoskeleton helps carry the various weapons and items he finds in-game, while a more magical environment, Neverwinter Nights or The Elder Scrolls IV for example, items like bags of holding are used*. In other games, mostly First-Person-Shooters, your character cannot carry a large amount of items - and thus it is more realistic - at least in that sense. Another way is to make your character unnaturally strong, as in Bloodlines, and so comparing his or her to a normal human is superfluous.
*It is worthwhile to note that the vanilla version of Oblivion did not include such items, but it was also hard to carry large amounts of items.