I think it also really depends on knowing your group and what they want to get out of it.
Very true. And part of any good writing for
any medium is to know your target audience and pitch your work accordingly.
For instance, I've got several players for whom one of the big joys of gaming is "interact with interesting people." Not to knock on their fellow players, but these folks don't want to have interesting conversations with only the same three other people in the game. So if they need an extra body along to smooth out fights, that someone should be worth talking to.
My players are definitely in that camp. They enjoy interacting with the NPCs as well as each other.
Out-of-combat, if the PCs want to talk to the guy, damn straight he's going to have a personality, and he's probably going to have a few surprises in his background or ambitions that reward the PCs for taking the time.
I've always tended to ensure that NPCs that are going to interact with the team on even a semi-regular basis have backgrounds, motivations and personality quirks. And if one that was designed to be a one-off encounter unexpectedly becomes more "regular" than previously planned - perhaps (s)he was helpful and the players decide to actively track down him/her time and again - and role playing dictates that the NPC become more three dimensional than the initial sack of stats I drafted, anything that comes out of the resultant ad-libbing gets noted down and the character is expanded.
NPC charts I've drawn up aren't quite as full-featured as the PC sheets, but they do have scope for a lot of stuff should I need it.
As I'm running as near to "Real-life Cyberpunk" as I can, I feel I owe it to my players to provide my NPCs with realistic motivations and - if required by repeated contact - human quirks etc.
Fortunately, I love creating character concepts and can do it on the fly. I actually think my characterisation skills are better than my plot-building skills.
And my players certainly do enjoy interacting with characters and nutting out what makes them tick - motivations and goals seem to be the big thing the players are concerned with (hardly surprising, I suppose, in a Cyberpunk game where the questions are "why would (s)he want to help me? Are they on the level or just trying to win my trust long enough to get me into a secluded, dark alley?")
I also like throwing in little bits from NPCs to keep the game interesting or teach the players valuable lessons like "don't make assumptions".
For example, I came up with what I thought would be a fun little quirk for their fixer that would make her more of a 3D human than a stat sack - after all, she's going to be a regular contact whenever they want to buy something - and also teach them the "dangers" of assuming things in a fairly safe manner.
They met the fixer - female, friendly demeanor, pink hair - and order some stuff. When they come to collect it, a bloke brings the stuff out from the storage area, fixer says "thanks, babe". Team assumes - as I had intended - he's her sexual partner and comment. She says, rather offhand, "no, he's Amber and Mona's husband". When they recover from the idea that he has two wives, one asks, "who are Amber and Mona?" and the fixer replies "Amber's my wife." Hilarity ensued while the team tried to sort out the marital arrangements.
In that little exchange I established the fixer as a
person with a life and a personality, conveyed the idea that the laws of this future are significantly different from the here and now (nice "we're not in Kansas any more" moment for the players) and showed them that making assumptions in my game is a silly thing to do - that knowledge may save their characters' lives some day...
Also provided a light moment and some enjoyable role playing. All in all, my little off-the-cuff idea that occurred to me a few days before proved quite successful.
Hell, last time I threw an NPC into a game because the two PCs needed a defender, the guy was stoic to the point of uncommunicative, and seemingly with no ambitions whatsoever. Perfect "don't overshadow the PCs" personality, right? For my players, it was like catnip: the PCs spent a lot of time trying to figure out what had got him that way, and how to light the fire of ambition in his chest once more.
Hehe, I can imagine that would be my players' reaction, too - sometimes it's best to give the NPC a quick and easy personality and motivations that the players can get a handle on in a couple of minutes and then get on with the adventure...
Thankfully, the character I need to run with this team was designed for an actual player to run - and has the same level of background info as any of the other player characters. This means that however far the
players decide to drive the interaction, I have the info on hand.
I'm not going to play the NPC as someone who keeps volunteering all sorts of details to the party and interrupting game play/overshadowing what they're doing, but if they ask a question of him, there's going to be an answer in keeping with the character.