One of the most complex RPGS ever, in both the best and worst ways. In short, its very good, but its not THAT good.
It's hard to explain what I didn't like about Chrono Cross without sounding like a nitpicker or a naysayer, so let me clearly establish something: I liked Chrono Cross. I liked it a lot. After all, there's a lot to like about it. It has good graphics, impressive character models, catchy music, great CGI cut-scenes, and one of the best battle systems of any Square game. Also, the interface is extremely well designed. Switching and equiping characters involves a bare minimum of annoyance since you can unequip characters who aren't currently in your party. Not only that, but there is some actual "role-playing" in this RPG, thanks to branching storylines and dozens of playable characters with backstories and optional sidequests. All your characters level up at once whether you use them or not, so if you decide that you want to use a particular character to complete his/her sidequest, you don't have to worry about getting stuck with a crappy low-level fighter.
Unfortunately, Chrono Cross has a few problems in the storytelling department. The story centers around Serge, a teenager who gets sucked through a dimensional hole into an alternate version of the world where he drowned when he was seven. As Serge, you have to travel back and forth between both worlds, uncover the secrets of time, learn your own significance, and, of course, save mankind. Its a good storyline, but its also damn near incomprehensible. At the best of times, you'll have a basic understanding but you'll wish the characters explained things in a bit more depth. At the worst of times, you won't have a damn clue what's going on. A lot of villains, schemes, and ancient artifacts are introduced on a need to know basis and with a minimum of explanation. However, once you get to the end, a lot (not all) is explained. I still have some questions, but I understand the story well enough to be able to say that it's actually pretty cool. I'd definitely recommend playing Chrono Trigger first, not only because its so great, but also because an understanding of CT contributes to an understanding of CC.
Another problem with CC is that sometimes it can be, well...dumb. Along the way, you encounter bee-type creatures who make bad puns, fairies who make bad puns, a minion named Ketchoo who shouts "Tomato", and a surfer/doctor who says things like "once she heals, she'll be able to hang 10". And let's not forget the part where a rock star has to play a song on his guitar to save an island from evil spirits (cue the long, cheesy, and woefully unskippable cutscene that I had to watch twice because my game froze).
Overall, I'd say that Chrono Cross will more than please RPG fans, but its not one of the best RPGs ever made. If it weren't for Square's preexisting RPG fanbase, I doubt the game would have gotten as much acclaim from critics or gamers.