Dragon warrior 1-4 were released for the nes a long time ago, all but the first are really hard to find though
Then 1&2 were re-released on the gb/gbc and #3 was re-released on the gbc, about 3-5 years back I think. And I have no clue when 7 was released, though I own it, it's been about 3 years since I've last played it, so I'll tell you what I remember.
The basic plot is that your fishing village is the only known island left in the world. Then one day while exploring, you find some ruins with your buddy, Kefka I think it was. Inside the ruins you find a broken map piece on a pedestal, and when you put it together you get teleported back in time to the location from the map. It's a depressing time for the village when you arrive, but once you make everything right again and return home, you find out that an island has appeared in your current time. So you go on a quest to find the map pieces to use on the pedestals in the temple, so that you can resurrect the other islands and find out what hapened to them.
I suppose this might be considered one of the 'better' Dragon warrior games, but I couldn't stand any of the main characters except for maybe Gaboo, Or whatever the wolf kid's name was, he was cool
The battle screen is the same as the previous DW games, so you can't see any of your character's on the screen while fighting monsters, unless you happen to meet a mimic or something.
One of the better features of 7, is that the class system is awesome! You get to mix basic classes to come up with advanced classes, then advanced classes to come up with master classes. There are also monster classes as well.
Hmm... You know, that's about all I can remember about this game at the moment
About the difficulty of finding a copy of any of these games... 7 would probably be the easiest to find, followed by 3, then 1 for the nes, then 1&2 for gb/gbc, then 2 (nes), 3 (nes), and 4 (nes).
Sorry, I didn't plan for this to be so long, lol