I've only played DQ8 and DQ11, but I found both fantastic, traditional JRPGs. Don't expect anything resembling post-SNES Final Fantasy. DQ is much more old-school. Typical hero in a medieval fantasy setting, pure turn-based combat and generally more simplistic stories, characters and gameplay systems.
DQ11 demands some patience at the start. It takes a long time to get going and combat can feel a little too simplistic initially. It does open up after a while though. Not that it ever gets complex, it just gives you more flexibility.
This simplicity is at the core of Dragon Quest and can be a positive or a negative, depending on your tastes. Some people will find it boring, for others it's comforting.