1. Dragon Quest 8 - Best DQ ever, hands down, no questions. Possibly the best jRPG of all time for that matter.  The game was just excellent from start to finish; small cast of compelling characters, beautiful graphics, amazing score, and the greatest explorable world ever.  Throw in the monster arena, great call back backs to previous games of the series, and Level 5's trademark alchemy system and you've got a list of elements that made a damned near perfect game.

2.  Dragon Quest 5  - The best story any of any game in the series.  One of the better stories to come out of the 16 bit era for that matter.

3.  Dragon Quest 9 - This latest installment broke a few traditions and created a few new online features that will hopefully be a part of the series for years to come.  It shook things up just enough, but at the core stayed true to all the important things.

4.  Dragon Quest 3 (GBC) - The GBC version of this game makes it the most polished old school jRPG you'll ever find. A large class system, an in-game board game, tons of bonus content, and 2 worlds to explore make this a must play.

5.  Dragon Quest Monsters - Fuck Pokemon. This game was the best monster trainer game for many many years. The breeding system, a large monster count, and tons of DQ nostalgia make this a game worth playing to this very day.

Yes, Monsters was the origin of the DQM series. The first was really good though because it was like a more complex self contained Pokemon and to date I think is the best of the sub-series.  The sequel went the Pokemon route with 2 cartridges and that kind of ruined parts of what I loved about it.  The third was just terrible and was more of a strategy game that tried to bring DQ7 into the main universe.  Then came Joker, which was kind of love it or hate. Personally I did enjoy it, and thought the flaws of it could be fixed. Still crossing my fingers we see Joker 2 over here.