So, having completed the entire Magical Quest trilogy, I can wholeheartedly say the games are worth a play.
Functionally, at their core, they play in a very similar manner, so if you like one, you'll probably enjoy them all.
Each subsequent game builds on something established in the previous game, from adding the co-op in Great Circus Mystery to then making both characters play a little differently in the third game.
Nostalgia be damned, the first is still my favourite.
I would recommend playing the #SNES versions as the #GBA versions suffer from screen crunch, and the #SegaGenesis version of Great Circus Mystery is a bit cumbersome on the 3 button controller.
I can't vouch for how good the co-op mode is in the game, but I can imagine they would be a fun time.
There is a charm to these games, and I think Disney/Capcom should definitely revisit these.