Yeah. After DQ11's ending looped to DQ1, I thought they were going to start over at the beginning and remake the whole series in the DQ11 style, which could have been amazing. Well, 2D-HD is cool too.
Originally DQ3 had the revelation about 75% of the way through that you're Erdrick (the "legendary hero" in the history of the first two games), making his pilgrimage down to the underworld to fight evil.
What I found most profound about it was that it turned out the world of the first two games actually WAS the underworld. DQ3 takes place on the surface world (our Earth, more or less). So throughout DQ1 and 2 you had no idea you were actually in our underworld, and Erdrick coming down to save their world was actually him descending from the real world into what they perceived as the underworld. I mean there's something philosophical about all of this, for sure.
While this was all a big revelation in original DQ3, I expect in these new incarnations they'll be pretty upfront about DQ3 being the first of the three and will treat 1 and 2 as its sequels, since most people are aware of this already.
As for the gameplay, DQ3 is easily the deepest of the three and the one I've played the most BY FAR. It's got class choices and you can form a party with whichever classes you want (the lead is always going to be the Hero class, so you can choose the other 3). However what gives it a leg up on, say, FF1, is that after about halfway through the game you can change classes whenever you want. The new classes start at level 1 with half the stats and all of the abilities of their previous class, so you can just keep leveling up different classes to create uber-characters. Like a soldier who has super-speed from being a thief, or a monk that has all of the white magic spells.
By comparison, DQ1 and 2 are more "regular RPGs". DQ1 you play as one guy (Hero class, so has both melee and magic), DQ2 you've got 3 (a fighter, a caster, and a jack of all trades). The DQ2 trio are the descendants of the DQ1 guy so his abilities are basically split between them. I expect DQ1+2 will be one big game since the two combined are a little shorter than DQ3, with the changeover happening midway through it with a "100 years passed..." type of thing.