I think there's been a postitive impact
Quest design
Pretty much everything I learned about sidequests I learned from CRPGs. What was cool and what wasn't cool. For instance, most players think Fed Ex quests (delivery quests) are kind of boring, but you do need them early in the game to introduce the PCs to new areas. It forces them to explore and the tiny exp you get out of a typical Fed Ex quest is a huge deal at 1st level. Hunting quests are more exciting, but you can't have too many or things get dull. What players like to see are quests that affect part of the game world, even for a little bit of time. The advantage of pen-and-paper is that you can make that impact permenant. I think this was best done in the Shackled City campaign. I won't spoil anything, but the map change is really cool and that's the kind of thing I think a lot of players like to see.
Magic Items
This is a lesson I don't think the pen-and-paper community has really picked up on. At least not the d20 guys. You can't fine tune a magic item in the core rules. Also, it's crazy expensive to add on flaws to magic items. How about a greataxe that is considered magic with no bonus to hit, does +1d6 fire damage, but imposes a -2 will save? That's a great low level magic item. Is it better than a +1 sword? The answer is "Maybe" and that's the kind of answer I like to see in magic items. I want my players to sit down and make a choice about loot. Magic items tend to have a lot more variables associated with them in CRPGs.
NPCs
The nature of a CRPG brought forth the idea of telling a story not about the players, but about the NPCs. For example Bauldur's Gate 2 was about Jon Irenicus' fall from grace and his twisted attempt to restore it by force. The players were basically nothing more than an involved audience. You need that kind of storytelling when you can't control who the PCs are. That's an ability a DM needs to involve players. Of course you can go too far and accidentally overshadow the PCs, but you still need to be able to get a story out.
Balance
CRPGs made it clear the importance of game balance. Look at the old 1e and 2e experience point tables. For some reason the wizard at the low-mid-level range advances very fast, especially when compared to a fighter. That's nuts. The ranger was a great class in 2e and to qualify for it you had to roll really good ability scores, so you already had an advantage. That's nuts. Wizards progressed in spell power while fighters' hit points leveled off. That's nuts. These problems became a lot more clear in computer environment because normally the DM fudges things around to cover up these things. A computer is a lot more unforgiving and the need for game balance becomes a lot more clear.
So, yeah, computer games rock!