Dragon Quest V is the peak of the Dragon Quest series in my opinion. While III and IV were huge improvements on gameplay and story and are definitely favorites of mine, V changed the whole game on all accounts.
The game begins much like all the others, wandering around a town and doing small quests to get a feel for the game mechanics. You explore with your childhood friends and companions (remember them!) until you and a fellow prince named Harry get kidnapped and enslaved for 10 years, bringing you to your adulthood. Strangely, you obtain a legendary sword very early on in the game. However, it cannot be equipped. Surely it will be equippable eventually, right? So, we stick it in the inventory for later. On your travels you re-encounter your old companion Saber, a Tiger-type monster who became friendly with you during your childhood, introducing the "monster catching" mechanic in the game. This is a huge game changer, inviting lots of new opportunities for party arrangement. Though by the end its fairly obvious that the game wants you to use a specific party, it's fun to be able to experiment with different combinations and abilities.
The setting is another standard medieval fantasy world featuring some of the expected places to explore, such as castles, caverns, volcanos, and deserts. But there are other worlds too, places like fairy land, the dark world, and a city of dragons in the sky. While I wish that some of the overworld settings were a bit more varied, these other locations keep the game interesting and make it fun to explore as much as possible to find other hidden places. Plus, I love the general layout of the overworld, being mostly built of isolated continents and islands for you to travel to one by one and tackle the different dungeons they each have in store.
The storytelling is one of the best of the Dragon Quest games, taking you through your character's life from childhood to fatherhood, introducing a generational aspect to the story that was really refreshing for a game from this time. While dimension-hopping and time-travel are prominent story beats, it's mostly your characters personal journey and trials that keep you hooked into it. You'll encounter anything from deciding who will be your "Heavenly Bride" to avenging your fathers' killer, losing to the villains to being rescued by your own children. The wild ride the game takes you on rarely slows down and keeps you guessing as to what will happen next. This entry was so beloved all around that it even got a (loose) movie adaptation on Netflix, and despite the interesting direction they went with it it's actually not half bad.
All in all, there is a reason why this game is near the top of most Top JRPG lists. It has the full package of what fans of Fantasy, JRPGs, and Dragon Quest could want: an interesting world to explore, characters that endear you to them effortlessly, any number of different playstyles to match each individual player and a story to match it all. While I still feel DQIII is the best entry point overall for newcomers, this is likely the game that will keep them wanting more from the series for years to come.