As was mentioned in passing upthread, Fallout 1 and 2 had very viable charisma builds. I played through both those games dozens of times with different character types, and the high-charisma character had a very different and still highly successful game. The dialogue was completely different, and you could influence the outcome of many situations using your charisma alone (my high-strength, low-cha, low-int brute character, by contrast, was pretty much forced to bash everyone he tried to talk to).
From what I understand, that is indeed the case. The way Fallout 3 implemented Charisma and Speech was really broken; my character has a Charisma of 1, but between tagging Speech and dumping a few points in every level, plus making sure I picked up every skill book I could find, I hit 100 Speech really easily. To make matters worse, because of save scumming it doesn’t matter how much Speech you have; if you’re willing to restart 5 or 6 times you can eventually succeed on any Speech check no matter how low. High Speech then only becomes a convenience.
That’s why most savvy players didn’t waste skill points on speech until the very final levels (or at least before barter, the only skill more worthless than speech), and ignored the charisma stat completely. And yes, from what I have seen there is now a percentage check done for speech (and other skills) in New Vegas.
Besides, you don’t have to have high intelligence to be a leader. Case in point
Honestly, I’ve always used Charisma as a dump stat, but that’s because I was playing games like NWN where you don’t really need to act as a leader and I don’t think you have to have high charisma to be a hero.
The designers of the SPYCRAFT rpg made explicit that they wanted to keep Charisma from being a dump stat, and did a pretty good job: if nothing else, it reflected how much pull your secret agent had with the agency when requisitioning covert-ops gear and calling in favors and so on – but it also helped that bard-type abilities got split up among various classes, so that even a straight-ahead military type would get the five-times-per-game ability to boost his own rolls and those of his teammates according to how charismatic he was (and needed a certain prerequisite amount of Cha if he wanted a Personal Lieutenant).
Of course, that sort of game also lends itself quite readily to playing a seductive con-artist type, or a master of disguise, or a well-connected guy who excels at bribes and blackmail; there’s already less of an emphasis on straight combat, since you’re supposed to be sly operatives who can get the job done à la the MISSION: IMPOSSIBLE crew. But even so, they worked pretty hard at making even tcat-burglar types or crackerjack snipers think twice before shorting Cha.
In GURPS, charisma is an advantage, not a skill. You either have it or you don’t, at three ascending levels. It affects reaction rolls, but really, it has to be role played.
The HERO system makes the distinction between Presence and Comeliness. I’m not sure if that counts as making it more or less useful - COM is usually considered not too important if you’re a combat-oriented type, but there are two whole stats that are physical appearance-based.
Presence is not appearance based. In fact, technically speaking Charisma in D&D is not appearance based either. In both cases it’s more like strength of personality, self-confidence, conviction, that kind of thing. Self-confidence can make a plain or even ugly person attractive, but it’s got nothing to do with appearance.
As I mentioned upthread, it is possible for the Nameless One in Planescape: Torment to have 18 charisma if not higher. This is what he looks like. Face shot.
It’s not that Charisma in D&D has nothing to do with appearance, but rather that physical attractiveness is just one of many aspects of it. Basically, anything that makes people more likely to react to you the way you want them to is part of charisma. Attractiveness certainly doesn’t hurt, there, but self-confidence, a strong, resonant voice, poise, posture, mannerisms, skill at grooming, a quick wit, and many other traits don’t hurt, either.
But yeah, it’s certainly not all appearance.
Strictly speaking, “charisma” means divine grace: it’s the measure of how much the gods love you.
True this. I remember TSR kept trying all the way up through 2nd Edition to introduce a “Comeliness” attribute to represent physical attractiveness, but it really never took.
What’s really funny about this post is he’s yelling this while the older kids are playing D&D. 
Well the problem with Comeliness is that it’s utterly pointless. It never did jack squat in the game. If you cared about beauty in your character, having a random die roll was annoying. If you didn’t, the state meant nothing to you anyway.
As I recall, the comeliness stat as introduced in the Unearthed Arcana (AD&D first edition) actually was ludicrously overpowered, at least if you had a fairly high score; I don’t think I ever knew anyone who played it as written.
Incidentally, an ultra-high Presence is one of the (many many) ways one can create a stupidly overpowered character in the HERO system (at least as of 4th edition).
Charisma will always mostly be a trash stat in CRPGs because computers suck at modeling interpersonal interactions. The best we’ve managed to date is some of this flimsy “some dialogue options may not be available to you if you don’t have enough charisma” thing, which, truthfully, doesn’t even begin to scratch the surface. Until we can model human interaction in some more elegant fashion, there’s not much that can be done for it.
On the tabletop level, it depends on your GM and your game system. In 4th edition D&D, charisma is a primary stat for some classes, which results in them using it for their TO HIT bonuses. It doesn’t get any more critical than that. In terms of actually using charisma for interpersonal interactions though, it gets hairier - its sortof like intelligence in that it’s hard to say when you should be using the character’s stat, and when you should be using the player’s ability. You can have a character with enormous charisma, but if you’re a fumbling, socially challenged individual, you’re really going to be relying on your GM to either give you die rolls to impress NPCs or to “filter” your fumbling attempts at diplomacy through the fact that your character is supposed to be a shining example of personal magnetism. It depends on how your group roleplays, to some extent too - whether it’s normal to say “I walk up to the guard and try to persuade him to let us in.” or "I walk up to the guard with a little grin, “You look tired, mate. Rather than have a long argument, do you think you could let a fella in to see his ‘sister’?” The former is more likely to be resolved by “Okay, roll bluff” while the latter is more likely going to be roleplayed out, possibly with dice rolls, possibly not.
How to handle this kind of thing is one of the big debates in the tabletop space, and there really isn’t a right answer - just “whatever works for your group.”
As an aside though, some game systems have started to “fold” charisma in with other stats, which produces a slightly blurrier stat system, but means that every stat has a distinct mechanical advantage as well.