Definitely a great show that followed the Batman and Superman cartoons of the mid-90's. The first two seasons featured Superman, Batman, Green Lantern, Wonder Woman, Hawkgirl and The Flash.
However, after an interesting plot twist at the end of the second season that occured in an amazing three part finale, Justice League Unlimited was created and hundreds of heroes were brought in.
Though very few episodes feature the majority of the charcters, those that do are amazing. One great thing though is that each character has a great background and personality so that when only a couple are focused on, the story is very interesting.

Some of my favorite eps from both shows were (warning, spoilers for each episode will be mentioned):

Justic League eps:
Twilight - Darkseid's return and possible death, plus we get to see Superman's darker and more vengeful side.

Injustice For All - Some great villains and a lot of great scenes for Batman, plus we learn that carrying Kryptonite with you is very bad, especially for Luthor.

Only A Dream - Batman really shines in this one and proves that he can really mess with the villains' minds...and even destroy them.

A Better World - Wow, this one not only had some great fights and a very interesting story of what could happen if the Justice League decided to cross the line between heroes and rulers; but it also featured one of my favorite line groups from the entire series (Between Batman and Alternate Batman):
"You grabbed power!"
"And with that power we've made a world where no eight year old boy will every lose his parents...because of some punk with a gun..."
"...you win."

Hereafter - Yeah they couldn't kill Superman off but damn was this a good episode and the reactions of the characters to it were very well done.

Wild Card - Joker's kind of like Batman, he has no special powers, but DAMN is he smart and unlike Batman, he's the most sadistic son of a bitch ever.

Starcrossed - You have to see this amazing three part season finale yourself, words don't do it justice (no pun intended).

Justice League Unlimited:
For the Man Who Has Everything - Yeah bringing back the guy from "War World" was kind of lame, but the scenes with both Superman's and Batman's "perfect worlds" were very touching and very realistic from both of their points of view.

Kid Stuff - This was by far the FUNNIEST episode ever. Seeing Superman, Batman, Wonder Woman and Green Lantern fight as kids and even act like kids was damn funny. Plus the lines were hillarious:
*Wonder Woman notices that she's taller than the boys* "I kind of like this."

*Everyone flies faster than Batman can run* "It's not a race you know."

*Wonder Woman catches Batman* "You okay tough guy?"
"Let me go I'm fine!"

*Wonder Woman walks up to Baby Etrigan* "Etrigan! You stop right there! I mean it! You naughty monster! Bad, bad Etrigan!" *Baby Etrigan starts to cry*

*Batman, after seeing Wonder Woman pick up Baby Etrigan* "You've got to be kidding me."
"He's just a baby." *She pats Etrigan's back and he belches fire* "That's all he needed."
*Green Lantern sniffs* "Ah man, that ain't all he needs."
*Batman back away* "Now that is a job for Superman"

*Wonder Woman* "I guess I'll go with Clark...*looks at Batman* Unless I should go with you."
"Whatever."
*Superman* "I'm fine to go with Diana"
*Lantern* "So Bruce and I are good to go?"
*Wonder Woman* "I changed my mind, I'll go with Bruce; and John can go with Clark."
*Batman, in an annoyed voice* "Whatever."
*Superman* "What's with them?"
*Lantern* "Man, for somebody with like, 50 different kinds of vision, you are so blind."

*Everyone is turned back to adults and Wonder Woman is holding adult Etrigan*
*Etrigan* "Mommy."
*Wonder Woman drops Etrigan*

But there was a great serious part at the end that was great:
*Batman looks at all the parents with their children*
*Wonder Woman* "Circumstances aside, it was kind of...enjoyable to be a kid again."
*Batman* "I haven't been a kid since I was 8 years old."

Wake the Dead - Personally I didn't like one of the episodes that this resulted from ("The Terror Beyond"), but it was a great return episode for Hawkgirl.

The Once and Future Thing (Parts 1 and 2) - Well done story and it was great to see Terry McGinnis return as the future Batman, plus Old Static was cool.

Doomsday Sanction - Ever since I found that the guy Alternate Superman lobotomized in "A Better World" was Doomsday I wanted to see him come back for a better role. Well I guess I got my wish. This was an amazing episode on multiple levels and to be honest, I thought Doomsday was gonna kill Superman up and until the end. Batman also got a very well done role in this one too.

Clash - Captain Marvel was interesting for a "use once and then throw away" character. The plot and the fight between Captain Marvel and Superman was very well done.

I like JLU a lot. I was giddy when I saw that new episodes were on the way (neither of which happens very often). But there are some drawbacks to the JLU. Mostly, there's no room for small-time villains like Joker anymore. Unless you've got powers (money being a power I guess) you're not cut out to be in a JLU episode. I'm just hoping there's an episode where the Justice Lords get their powers back and go medievil on the JLU.

Yeah but the Justice Lords would be so outnumbered it wouldn't even be funny. Plus it looked like the alternate Batman was turning against what the Justice Lords had done.

The seven of them conquered Earth on their own. Don't you think they'd have a plan to fight other heroes?

True, but this time they'd be outnumbered by super heroes; oh and it wasn't seven, it was six, remember, their Flash is dead.

Oh right. I doubt the entire league would go after them at once. This isn't AMAZO.

True. Though they could just go: "Amazo, they said they're evil, have fun!" Haha!

But I'm very curious as to how this season is going to play out.

I don't like any of the heros but Batman anyway, it's a decent show but doesn't interest me much.

Its a great show, But I keep missing episodes. Which really sucks, I dont know how many episodes I've missed or how many episodes I've seen. Although yeah, Clash was great.

Limewire has episodes that haven't aired yet...I'm currently downloading the second to last episode... ^_^

Mmmm...limewire. Isn't that a mixed drink?

Its a Kazaa like service thing. AND DAMN YOU VINCENT. YOU CHEATING BASTARD.

You're just pissed cause you don't got 'em.

EXACTLY.

Final ep isn't on Limewire yet...grrrr.

Grrr. Too must watch seen those other episodes.

Must see "Epilogue," must know what happens...

I'll bet you it involves the justice lordsl.

Justice Lords techinically don't come back. When you see "Divided We Fall" you'll know what I mean by "technically."

Just watched the finale...and it's possible for them to make another season, or series...oh and they reveal the BIGGEST plot twist I've ever seen anywhere. PM me if you want to know what it is. (Oh and it doesn't not involve the Justice Lords)

I dont want to know. But damn, Who woulda guessed that Luthor would 'hack?' the thing and have 'em shoot the place lol.

Wait until you see next week's ep; it's awesome.

WAITING IS FOR FOOLS. Thats why Im going to time travel to the future and watch the episode!

Either that or ask Jamie. He lives in the future, you know.

Or download the ep off Limewire. The title is "Panic in the Sky."
It's freakin' awesome.

OLOL So all the panicing people grow wings and start flying, so they panic, in the sky? LOL Cool.

More like at the Watchtower...

Shhh don't spoil the plot point where <Insert Plot Point Spoiler HERE>! and that <Insert even bigger plot point here> Don't ruin it for the other Forum goers.

SO DO I!!!!!! But in temrs of shows we are FAAAAR in the past.

.....wow. Brainiac? I did not see that coming.

Me either. Total curveball, but it does explain the superstrength.

Neither did I, but this was the first episode of this I've ever seen.

I thought thsi episode was already aired with teh SuperGirl vs. Supergirl action going on. Then again I don't watch JLU very often^^

<Green Arrow> WHOO HOO! Go for the fabric Super Girl!


>.>

You're a bad man, Arrow.

Maybe, but that's definately what he'd be thinking.

Heh, yeah the Braniac thing threw me for a loop too. Don't worry, it will be explained in the next episode.

Oh and wasn't that massive fight on the Watchtower freakin' awesome or what?

Definately cool. But if you watched Superman and/or Static Shock you'll know what it's about.

I've seen Superman and I know when Brainiac and Luthor became "one" after they talked about it in the next ep. I've barely seen any Static, though I did see the one episode in it with Superman and it has nothing to do with Luthor or Brainiac.

Brainiac pulled off his trick in a second season Superman ep entitled "Ghost in the Machine."

Actually the first time JL and Static teamed up, Brainiac did get out.