As the poll reflects, at least as of now, the Chrono series is not about one thing (I think it could have been had it really well developed the characters in Chrono Cross...but let's not stray...). What makes it so great is that it's a powerhouse, a creative force. It has many great things going for it that even if you didn't like one aspect, you're still likely to like several others.
Take myself for example: I didn't like the Character Development in Chrono Cross (holy hell...It always seems to come to this with me, doesn't it?), but I absolutely loved the storyline, the gameplay was solid enough, the music was top-tier, and the graphics were up-to-date. Radical Dreamers is similar: although it is, of course, lacking in any graphical sense, it makes up for it with really well rounded characters, easy gameplay (I think it's fun even if no one else says so), and a really nice story. Each one of the games excells at Replay Value in a genre (RD kinda skips out of the RPG genre a bit though) that really isn't known for it.
I voted for the Characters because Crono & Co are really what got me hooked, right from the start.