I've played through the mobile versions of all three games.
For a short description, the first two are fairly simplistic, while DQ III has enough features to the point everyone would recognize it as a JRPG.
Any way one looks at it, these games are true classics. In fact, it could well be argued this trilogy effectively shows how the JRPG genre came to be. So the games are definitely worth preserving.
Although, as I've stated before, I highly recommend porting of remake versions of the games rather than the NES versions - the remake versions have not only better sprites, but sometimes additional features the original version lacks.