Early ComputerRPGs tended to be dungeon/maze crawls, where you ran around dungeon (maze) where all the walls look alike and you need to map things out or else get horribly lost. They also had the same kind of turn-based menu-select battle system that ConsoleRPGs do, but most new ComputerRPGs don't. This may be at least partially due to input devices such as mice that allow a simple but adaptable interface without being too slow and cumbersome. There is a sort of spectrum starting with FinalFantasy-style menus on one end, then overhead tile/menu based games like SaiyukiGame and FinalFantasyTactics, then overhead map games like Fallout, NeverwinterNights?, and PlanescapeTorment. A few of the newest ComputerRPGs, such as MorroWind and DeusEx, have switched to FirstPersonShooter? type views. And BTW, FirstPerson? sucks. :P -SeleneTan
Many ComputerRPGs are either based on an existing RolePlayingSystem (e.g. the DungeonsAndDragons games) or have systems that are so well-defined that they could be turned into tabletop RolePlayingSystems (e.g. Fallout).
BlackIsle? games such as Fallout and PlanescapeTorment place a greater emphasis on quests. Although you gain experience for fighting monsters, you also gain a LOT from doing quests, possibly more than for monsters. (Well, er, for a reasonable amount of time spent on monsters.) Unlike in ConsoleRPGs, if you talk your way out of a fight, you will probably get as much (or more) experience as you would have by slaughtering your enemies.
Other games such as MorroWind replace traditional experience-points with improvement by actual use of the skill. In general, the mechanics of ComputerRPGs are much more varied than the FinalFantasy hack-and-slash game systems.
ComputerRPGs tend to emphasize World, then either Story or Character, and then the last of the three. They tend to brag about how many locations you can explore and how many things you can do, rather than how many hours long the movie-esque storyline is. Typically ComputerRPGs offer more room for controlling the personality and actions of the characters. They also tend to stress the importance of the player in not just numerically improving, but developing the character. (e.g. you can threaten someone to make them do something, or you can ask nicely, and it actually has an effect beyond giving you extra items.) They're still fairly linear (as are most games), but at least there's more than one way to solve most problems.
AlexBobbs will note that while allowing control for personality and actions is a worthwhile goal, he has never been impressed with the actual implementation in any ComputerRPG. There's a strong tendency for it to still not really matter that much (aside from getting XP), and even in games where it does (Fallout, sorta), it's constrained by the limited choices. In some ways, character interaction reminds me of those "Choose Your Own Adventure" books: the choices you want are often missing, and the "correct" choices may be something you never would have thought of if the game didn't push you in that direction. In the end, I've always found it more fun to just fight your way through everything.
SeleneTan doesn't like ComputerRPGs quite as much as ConsoleRPGs because she gets lost easily, and ComputerRPGs usually do less braining you with a two-by-four labelled with the location of the next quest in the plotline.
Contrast with ConsoleRPGs.
This node probably NeedsRewriting and additional commentary. Comments based on wider selection of games would probably add insight.