Take Sword, Add Protrusions
There must be some kind of law about fantasy swords in video games. There's a recipe to them, if you know what I mean. It's not enough for a sword to be a long piece of sharp metal. It's got to have... extra stuff, extra colors, extra everything! Presumably this is because normal swords are boring, or something. I can't quite fathom why various different blades designed purely to kill people real good might be considered boring, but there you have it.
Take the basic sword concept, i.e. a flattened length of material of three to seven feet or more depending on your personal level of comfort with absolute silliness. No need to make it straight - any line that meanders around and eventually goes from point A to point B will do.
Consider the type of material. Metal, wood, energy, ice, dark matter. This can be anything that can conceivably be formed into the usual flattened sword shape, whether by magic or advanced technology or whatever.
Choose a random justification as to why this particular material can be used as a sword shape and might be able to cut like a blade should, usually in defiance of any kind of sensible scientific theory or basic common sense.
Add flashy colors or lights, in whatever pattern or aesthetic is required by the art department. They should follow the general reasoning behind why this material can be used as a blade etc, but don't feel constrained by that. You can and should go nuts.
Add a hilt. It doesn't have to look comfortable. It doesn't have to have a pommel, or a crossguard, or even be attached to the actual blade. Bonus points if you design a hilt that can't be wielded by anyone with normal hands without hurting themselves.
Add protrusions. Spikes, knobbly bits, random stuff that sticks out everywhere in all directions, stuff that floats around the blade at random angles. A million bonus points if the protrusions are all but guaranteed to hit the wielder if they do more than hold it out in front of them.
End result: swords that look like these.
To be honest, these shapes stretch definition of 'sword' to a maximum. But these are from a video game, and yes, it's almost expected that the weapons will be so incredibly silly that the players might as well be hitting each other with colored-paper-and-LED-light-festooned sticks.
It's all about why you have weapons like this.
The Purpose of a Blade
If you'll allow me to wax philosophical for a moment, let's examine why the relative silliness of weapons increases in video games.
Obvious answer: because they 'look cool' and the players want stuff that looks cool!
And I totally get this. Consider MMORPGs like World of Warcraft, for example. Part of the game theory that makes it akin to hard drugs on the addiction scale is the impression of improvement and achievement, and this is accomplished by way of leveling up the player avatar, completing quests or other objectives, and - most importantly - gaining the visual indicators of accomplishment. Most of the weapons above are only attainable by dint of extreme effort, through the expenditure of time or the application of skill. Many take months to acquire, or plain luck. Once a player has them, they can now show off an immediate visual cue that advertises that effort to other players in the world, and thus gains them in-game respect.
To a lesser extent, non-MMO games use this same psychological trick to keep the player engaged. They have a vested interest in keeping the player's attention, as this directly translates to sales; notice how much emphasis there is on flashy graphics for most modern triple A titles these days. The only one I know of that even vaguely reins it in somewhat is Dark Souls.
But outside of video games, for the most part, we don't see the same level of complete nonsense. There are still many offenders - the snap-together blade belonging to the Kurgan in Highlander, Conan's teeny little Atlantian sword (seriously, why didn't someone give him a proper longsword?), the six-swords-in-one wielded by Cloud in Final Fantasy: Advent Children. And of course, lightsabers. These weapons are nowhere near as ridiculous, and that's not because Hollywood is more restrained than the video games industry. Trust me, if it made sense for them to go as nutty as game designers do, they would.
The Importance of the Medium
Really what I'm trying to get at here is that the medium makes a difference. In a live action movie or TV series, it's because the medium requires the use of actual physical objects that can be held and moved through space by human beings. But notice that, even when physical sets etc are not a concern, a medium that's heavily invested in the narrative above all else tends not to go for the whole 'flattened, dubiously straight shape covered in sparkly bits' routine. Most swords that come from a non-video game fantasy setting are normal, for a given value of normal. Why is that?
I think there's a few reasons.
The first is the level of importance and attention ascribed to the weapon. In a narrative-driven structure, especially in a time-limited medium like a movie or an episode of a TV show, the relative importance of each element in the plot directly translates to how much screen time it gets. Now, it's possible to write a plot that makes a sword important - see The Sword in the Stone; Crouching Tiger, Hidden Dragon - but you'll find that the plot is less about the sword, and far more about the wielder.
Swords are still largely inanimate objects, and narrative is driven by animate objects like people, animals, talking cars, that kind of thing. It's more important to show the strike made by the master swordsman than it is to show the level of intricate detail on the blade making it, because that's what holds our attention in a time-limited medium.
Video games, though they might be narrative-driven, don't have the same kind of time limitation. They do have large stretches of gameplay where the amount of time the player takes to complete a section is unknown, and, in that case, flashy weapons and even flashier moves are part of what keeps the player's attention.
The second is, again, related to time limitations - that of competition in a given scene. Imagine, for a moment, that Highlander had been filmed with one of the swords in the picture above. Who would we, the viewers, be looking at? The actors, or the swords? Answer: we already know from looking at the Star Wars movies. Lightsaber battles are completely overshadowed by the lightsabers themselves, to the point where the actors are almost entirely backgrounded by them (with some notable exceptions, i.e. Luke vs. Vader in The Empire Strikes Back).
The flashier and more silly a sword is, the more of our attention it holds. This is desirable in a game sequence where narrative is not always taking place, but far less so in movies and TV where there can be no breaks in the narrative. The whoosh-flash-twirly madness of video games slots in perfectly as part of the player's engagement with the game, but it's woefully distracting and out of place in a medium that can't use gameplay as engagement.
Hollywood and TV tones down the silliness of weapons because it makes the products of their medium worse, whereas the same silly weapons in video games makes them better. Though we can spend hours criticizing said silliness as being unrealistic and ludicrous, we have to recognize that these weapons do have their place - and perhaps we should be criticizing them only when they're used badly.