Aside from its art style and enemy designs, there is literally nothing unique or interesting about Dragon Quest. It is the most generic, by-the-numbers JRPG series ever made.
Absolutely and utterly disagree with this statement.
The first 5 games alone offered things that had never been done on consoles before in JRPG's, so I'm not sure where this take comes from.
1 was the original JRPG on a console.
2 introduced multiple party members and enemies in combat
3 introduced the character class and job system
4 introduced the chapter and multi character perspective
5 to this day has one of the most unique methods of telling a story of any JRPG, let alone game, period. Never mind the monster caching element that was... 3 years before Pocket Monsters was even a thing in Japan.
And the games onward have continued to build on the foundation based on mechanics and designs such as this. Dragon Quest 9 was definitely one of the most unique games on the DS at the time. Did any other turn based JRPG's allow you to pair up with multiple friends and take on dungeons on a handheld at the time? Feel free to correct me and let me know, as I don't know of other games on the system that did that at the time. Hell, even DQ10... is there any other MMORPG's that were on the Wii at the time? Dragon Quest 11 S has literally 2 vastly different versions of the same game within. Do any other console JRPG's do this?
This isn't even taking into account the multitude of spinoffs and side games like Torneko's Dungeon, DQ Monsters, DQ Swords on the Wii or Heroes and Builders on modern consoles. While these concepts aren't unique in themselves in many of these cases, none of the inspired original works have the DQ charm or nostalgia that is a trademark of the series.
Dragon Quest shines because it gradually improves and respects it's audience. It is arguably the most consistent franchise I can think of in terms of quality games, since even a bad DQ game is still *good* and worth playing, I find. I like Final Fantasy as well, but it's kind of the opposite of DQ and is often all over the place in terms of what they want to do with it.
Oh, and to answer the question of the thread...
1) Dragon Quest III- The ultimate classic JRPG. Enix perfected their formula here and it's infinitely replayable and a classic for the ages. Legendary.
2) Dragon Quest XI- A love letter to the entire series up to this point and is like Dragon Quest 8 in terms of presentation but for modern day sensibilities. You can't go wrong with this.
3) Dragon Quest V- Never played this until 2009 but it's got one of the most intimate stories in all my years of playing games. It floored me that this was a game from 1992. Top-notch.
4) Dragon Quest IV- The chapter system was something never done before and for the first time on the NES, we had DQ characters with personality more than "YES" or "NO". Massive game at the time. Best 8-bit JRPG, bar none.
5) Dragon Quest IX- Spiritual successor to DQIII, it took the job class and ran with it for leaps and bounds. Downloadable quests, each item and equipment piece is reflected on your character, local multiplayer with friends to help beat that one hard boss... The story was touching and simple enough, but the real meat is the post game stuff that can last you for hundreds of hours. Best game on the DS for me.