Most of these are must plays
In addition to a new iOS and Android Dragon Quest game, it seems as if Square Enix has something more exciting up their sleeve -- ports of Dragon Quest I through VIII! Although they haven't been confirmed outside of Japan, this is a great way for people who haven't been able to wrestle up these classics to be introduced to them in some form or another.
Though I think some ports will lend themselves to the mobile platform more than others (I-IV should be perfect given their simplicity), I would be interested in trying out pretty much all of these.
Dragon Quest [Square Enix]