I think the more organic the dialogue system the better. What I mean by organic is that the actual human player is deciding on responses and the choice of response determines success instead of stats. Options can still be gated by stats some of the time, but can also be gated by in-game research. So if the player has taken the time to read some in-game lore, to talk to minor NPCs and find things out, he'll have more options in a conversation. Options can also relate to missions the player has completed and areas he's explored.The reason combat is inherently more fun than dialogue (at least to me) is that combat provides multiple routes to success and multiple levels of success. Did you win without anyone getting killed? Seriously hurt? Hurt at all? Did you win without using your grenades? Etc. Dialogue is almost always binary. Either you got what you wanted or you didn't. Boring.As an aside, quests are also often completely binary. If a player fails a quest, he's likely to reload and try again. I'd like quests with three levels of completion, or which give you a different but not totally negative outcome for "failure".