Why are JRPGs so much longer than WRPGs?

[RealRT]

Elaborate then, if you don't mind. Characters: What were some good characters?

Battle System: If on the off chance I WERE to give the Witcher 2 a chance, please explain how I would play as a meleeing spell-caster.

Colorful Areas: Again, please elaborate.

Comphesensible Plot: As a guy that hasn't played the games, and might (I'll say that again, MIGHT) start via the first or second, please explain the plot, so that I may have some clue what's going on.

Geralt himself is a fairly good character - a philosophing monster hunter for hire who has a bone to pick with destiny and who tries to reclaim his identity.
Dandelion/Jaskier - a womanizing bard, who is mischievous, but is very loyal to his friends and is actually pretty smart. There's more to him than meets the eye.
Zoltan Chivay - a dwarf war veteran who is also prone to philosophizing in his own way.
Vincent de Meis - captain of the guard of Vizima city, there's more to him than meets the eye. (1)
Thaler - appears to be just a fence, but in reality he's something else. Has some hidden depths you can reveal if you talk to people about him. (2)
Ziegfried - member of the Order of the Burning Rose, a knight. A nice guy who genuinely believes in knights doing good and provides contrast to Geralt's cynicism.(1)
Vernon Roche - leader of Temerian special force squad known as The Blue Stripes, that specializes in black ops and dealing with non-human terrorists. Pretty smart and badass, has some charm and a some depth to him. (2)
Iorveth - leader of Scoia'tael, the non-human resistance movement. Ruthless, but also loyal and can be a good friend (2)
Battle system: in both games Geralt primarily relies on his swords. The signs - the Witcher spells - play a supporting role. You have five signs in the first game and get another one in the second. Aard knocks enemy (or enemies) away, Igni burns them, Quen makes a shield for you, Axii makes enemies fight for you and Yrden leaves a trap on the ground. They can be used at any time once you acquire them, but deplete the Endurance bar that's like a mana bar. Also, in 2, depleting Endurance bar makes Geralt's attacks weaker.
In the first game, the swordfighting is like a rhythm game. You initiate the combo with the first strike and then press them at the right time by looking at the icon at the screen to prolong the combo. Should you do it too soon or too late, you break the combo and have to initiate it again. There are three combat styles - the Strong style, the Fast style and the Group style. Strong and fast work when you have to fight a single opponent and there are visual clues as to which style goes with which opponent - more lenient enemies go better with quick style, while Strong is better against big opponents. Fighting them with a different style, while possible, is harder, as combos break often and may fail to initiate. Group style works with either type, dealing more damage, the more enemies surround you.
In the second game, the combat is more action-based. One mouse button controls swift strikes, the other strong strikes. Again, which work better depends on opponent. There is more emphasis on blocking and rolling, there are reposts and the like. Hitting the back gives you (or the opponent) a critical hit. The signs Quen and Axii play a bigger role here and are more useful than in the first game (Aard and Igni, the most useful signs of the first game) were nerfed.
Colorful areas:

Spoiler

1

2

Those screens don't really do the games justice though. I'd make my own screenies, but my current PC struggles running Witcher 2.
The first game:
Geralt, a witcher (mutant monster hunter for hire) was found amnesiac (I know, I know, a cliche, but it serves to introduce the player to the setting) on the outskirts of Kaer Morhen, the fortress of the witchers, to big surprise of his four remaining colleagues, since Geralt died five years prior to the events of the game (in the books). Some days after his arrival, an attack happens in which a young witcher Leo gets killed and all the mutagens and recipes used to create witchers are stolen. Geralt and the others go their separate ways, going for the attackers, but on his way to reclaim the stolen mutagens, Geralt gets to unveil a conspiracy.
The second game:
After Geralt saves Foltest, the king of Temeria in the ending of W1, he is made his temporary bodyguard. Unfortunately, a witcher from a different group kills Foltest and sets Geralt up, so he's got to clear his name and learn who was behind several recent regicides and was also responsible for the events of the first game. Notably, the game splits in the second third and you get to play a different version of Chapter 2, depending on which character you side with.
Both games have morally complex dilemmas that, unusually, do not present momentary rewards or punishments, instead they bite you later.

 

[CriticalTortoise]

I never really noticed a length difference, but that's also because I don't like JRPGs very much and far prefer Western-style RPGs, and therefore haven't had much experience with Japanese games outside of the sort of canon of classics (Chrono Trigger, Final Fantasy IV, Star Ocean, etc). However, if there is a length difference it's most likely that JRPGs are a single story, designed more or less to be played once -- see it once, you see the whole story. That's not to say they never merit second playthroughs -- far from it -- but simply that the game itself doesn't change. Western games are designed specifically with multiple playthroughs in mind, and therefore to fit more alternatives and sidequests and choices into the data allowance, the game probably has to be a little shorter, otherwise art assets have to be reused or other things like that.

 

[Hawki]

The idea of repeat playthroughs is one I haven't considered before. That said, it's probably another reason why I tend to like JRPGs more. I'd much rather be able to do everything on one playthrough than have to go back and replay the game. Whatever choices a game like 'Mass Effect' might allow, there's still swathes of gametime that'll be the same on every playthrough.

And like Extra Credits, I'm starting to think that there really needs to be better terms for the different playstyles. 'Dark Souls' is more WRPG than JRPG, 'The Third Age' and 'Sonic Chronicles' are more JRPG than WRPG, etc. (using personal examples).