In response to maggiekarp's post I'm doing this solely by what's the official, the original. Only thing I'll add is stuff from the DS version(which is little to nothing). Plus I haven't seen ALL of Crimson Echoes yet, and I don't want to judge them by where I am now only to decide later I've changed my mind.
1.) Crono - He's the main character. Always been a sucker for them main characters. Where as usually silent protagonists don't work very well, they can be drab and boring, Crono gets it right. Because Crono helps show us "Silent Protagonist" doesn't mean "Emotionless". He's willing to risk life and limb for his friends and even for total strangers! What other bold badass is gonna see a girl he doesn't know anything about go through a blue vortex and take the chance of following her even though she COULD(and did) tiem or travel or maybe she just got shredded to little pieces? Crono'll face those odds.He'll face down the apocalypse itself knowing he's gonna die(SPOILER! NOT!). And in the standard ending where Gina gets sucked through the gate last second, we see one of the funniest things a typical hero can do... "Oh no! that gate'll never open again Crono!" "... *strike a BOO-YA! POSE!*" Next, the whipped cream! Crono's fighting style seems to flow so well. Back then, how often did you see Lightning heroes? Crono was unique and he's inspired a new generation of electric characters being one of the originals. Just hearing Luminaire for the first time is breath taking, practically makes you feel you're there, wind blasting past you holding up an arm to block the rays watching everything caught inside freeze for but a moment before it flashes away along with said enemies. Crono's got some sword skill to boot! Combine with all of this his not often referred but done enough friendships with his teammates, although the screen says that Crono is mute, you know all too well he's saying something. it's left off for a reason. You gotta love Crono because in truth YOU are Crono! What Crono feels YOU feel! What YOU say Crono says! When YOU obliterate all in your path Crono obliterates all in path! And so the story goes...
2.) Magus - Oh boy... here we go. Magus gets up as #2 for me since he seems to have more story than any of the other characters despite being a secret character! You know something's up and worth checking out when a game makes a hidden feature one of the best features of the entire game! Magus' techs are incredibly powerful and just as amazing to watch. The battle with him is intense and very memorable. The scythe makes him all the more frightening, as though he IS death. But in actuality he is a hero just with darker methods of victory and justice. Not getting the girl? Trying to push away all signs of emotion? Badass is a phrase that has been taken and abused nowadays. Now what I just listed are traits of a real one. Magus fits these traits. Magus really is a badass. Magus gets an incredible theme song that is one of gaming's most memorable songs ever. Magus' desparate search for Schala and protecting her from the events he ironically helped lead up to is both a sad, and enthralling tale that you can't deny getting caught up in. He's a character you want to hate, but once you realize you can get him and all he's capable of, it just becomes impossible.
3.) Frog - Frog has the true hero's tale. Even his song screams his sad life that leads to his epic triumph over Magus. Putting aside his sorrows to finally take on magus at his castle is already enough to earn him #4, what wraps it all up is when finally presented with the opportunity to kill Magus, his sworn enemy. The one sealing away his human form, the one who killed his best friend, he does what is possibly more awesome than Magus himself. He scheathes his sword and tells him that killing him won't do anything, he's not worth it, and he just walks away. Revenge I know from personal experience, especially life ruining revenge is incredibly difficult to deal with. much tougher than anyone thinks it is. It's about as challenging as getting tangled in barbed wire and getting out. Finding a hay in a needle stack. Taking a beating for 3 straight hours and living through it. Losing the love of your life. Losing both your parents in a car accident. Go through those, you may know how mentally difficult revenge is to deal, like a cigarette. Being the wielder of the Masamune isn't easy, but the way Frog pulls it off, Sephiroth's got nothing on him.
4.) Marle - I know this is where CERTAIN PEOPLE would disagree and say "Aww, you had such a good list going and then you did this." Well, this is MY opinion, post your own. Marle may not be the first but she was my first. Plus unlike most other princesses dealing with the issue of castle restraint, her father is more strict to the point of claiming terrorists are behind it and she's mind controlled. Some may say she complains often or seems stupid about things, but let's face it. How would you react to all this time travel? Way I see it, Marle is the realistic perspective on the adventure. Get used to it eventually and be amazed by the whole thing but at the same time, the different cultures, the way some of the people treat them, she has no idea how to behave. She puts up a brave front to hide the scared little girl inside, confused about why all of this is happening, especially since she's always had the castle life and has had the dark truths of the world hidden from her. As the adventure progresses she slowly but surely develops from faking her bravery for the sake of her friends and to not hold them back to actually making that courage a reality. The castle has kept her a child her whole life but by going on this adventure and seeing the world for what it really is side by side with Crono, she experiences fear, anger, joy, love. She isn't immature or stupid as everyone assumes. She's been contained her whole life and we're seeing her grow up. The climax of her growth though occurs in sadly a side quest(why she isn't as high)where she's learning the man she's hated for keeping her contained, her own father, is being framed and is to be killed. Her crashing through the window is almost like her blossoming into a full grown woman. Notice how she as the game goes on she gets less and less foolish in her actions but more wise and thoughtful. She's our little girl, behaving how we would if we were faced with death around every corner.
5.) Robo - Robo. The robot. If you're doing time travel you've gotta do a robot. Robots are generally the emotionless character with the cold truth perspective on situations. Robo changes this. Robo has some personality. In fact, Robo is one of the lighter themed characters of the game. Until his side quest. However now that we're lower in the list I guess I'll say the reason he isn't as high, it's cause the majority of him you get as a side quest instead of in the required game. I don't have as much to say here.
6.) Lucca - Lucca. She's got a lot going for her. But I never found her as interesting. Going by JUST Chrono trigger, she doesn't have as much going for her as the others either. She's got her backstory where she saves her mom's legs, but that's a side quest in a side quest. And on top of that, as sad and shocking as that mission is, it just shows what made her a scientist. Does she have any sort of deep story for her now that she is one? Not much of one until Cross then apparantly inbetween the 2 games she gets a lot. But that's not trigger, that's moreso Cross. So Lucca goes lower.
7.) Ayla - Short and simple. Backstory? Barely.
Alright now I'm going to go eat.