Let me preface this by saying that I know that many forms of media "borrow" ideas, or are inspired by other things. However, Fantasia
—from its uninspired title to its uninspired characters—tends less to borrow things than directly rip them off.
Case in point: the "heart keys" from the first game are basically Keyblades
, up to and including the fact that they can be used as weapons. Thanos is basically Oswald's Nobody, having been created when Oswald gained a physical form, akin to a Nobody being the former shell of a particularly strong person after their heart has been destroyed/eaten/whathaveyou and thus offering a hint of duality... that never gets followed up on
There are also the characters who resemble characters from other works
in terms of either appearance or personality (Nazim is pretty much a less complex, elven Guy
), although that is a bit excusable since it's just the author offering some Shout Outs
to her favorite shows/games/whatever.
But about the author not following up on interesting plots: it happens a lot
in this series. In fact it happens right from the get-go, introducing Cheryl as a tormented soul who has to help heal another tormented soul in a different world. The only problem here is that it instead turns into a happy-go-lucky romp through a perfectly safe "fantasy" world where no one hurts her and no one really wants to—except for some incidental guys who get defeated by Leon in Ian's route. Oswald's route is intriguing until it turns into the typical schlock of Cheryl "healing" him and being his calm, caring girlfriend while taking a lot of verbal abuse and trolling from him. Heck, Oswald himself is pretty cool up until you get to his route, where he goes from being kind of cool to being your typical Jerk With A Heart Of Gold
My main beefs with this series are basically that 1) Fantasia itself is boring and doesn't feel like a real world with a real history and 2) the characters are all dumb, in terms of actual character and wit. Also, none of the jokes are funny.
Now, "good" is, of course a relative term. You might like it. But don't get your hopes up going into it if you want something that isn't a complete Cliche Storm