The Chrono series is a series of games (mostly known for being high quality RPG games). The release of a new game in the series is rare, and some can argue that because of this, they are more anticipated than the latest in the Final Fantasy series.
The main games in the series, so far, have connecting plots but different characters. The main theme is travelling beyond our realm, whether it be to different times or different dimensions. The consistent "Chrono" in the title implies that time travel, or the effects of it, will be the focus of the games to follow.