You know what's really annoying about the Mana series? The later games could have been much better, if they had just put a bit more effort into them. Dawn of Mana needed to get the camera and level-up system fixed, Heroes needed to deal with the path-finding issue and Children...admittedly that one was just kind of mediocre. It wasn't bad though. Fun for what it was.
Heroes had a pretty good plot, and it set up SD3 pretty well, but the gameplay was clearly a tech-demo for FFXII: Revenant Wings, and Dawn had some good ideas but awful execution. Again, Children of Mana seemed to be exactly what they were aiming for, they just didn't aim very high.
Square Enix just kept phoning them in.
That's what compilations are though, a bunch of low effort games developed all at once, and the World of Mana compilation was bad, even by compilation standards.
Also, the series seems to be deathly afraid of getting near Secret in terms of goings ons (either clinging to FFA or SD3). Its like the Zelda II of the series.