I'll be honest with you, Dragon Quest 8 on PS2 was my first experience in the series, and it wasn't a good one. I've been playing RPGs since the NES days, and I've played a lot. I bought DQ 8 on the positive reviews, but found it much too limited in scope, the story rather mediocre. It was a bit too much old school for me. After playing it for a few hours, I abandoned it. Many gamers told me that I 'simply didn't get it'.
They were right. Some time ago I suddenly craved a traditional RPG to get the bitter taste of Final Fantasy 12 out of my mouth. I popped in DQ 8, and I fell absolutely in love. I fell in love with Dragon Quest 4 as well, and when I started playing it I was struck by the little evolution between this entry and number 8. Basically, DQ4 is the oldest of old school, and pretty hardcore to boot. The plot is straightforward (the Chosen One must prevent the rise of the Dark Lord), but told with so much charm, risque humour and colour, that you'll love every minute of it.
There are some downsides, though. The Chapters idea is pretty good, but if you have to start from level 1 for fourth time, fighting the same monsters and buying the same equipment again and again, it starts to drag a bit. Things pick up though when all the characters join in their mutual fight. It's not as complicated as Final Fantasy (dungeons are extremely small, the story is linear, not many sidequests, no hidden optional skills you'll need a player's guide for to achieve), but you can take that for a plus or minus, depending on your taste. Also, there's not much variety in the monsters, they are composed of a limited set only set apart by differing colours and names.
One extra plus, this is a great game for RPG newbies to start with. Final Fantasy, especially the later and weaker installments, can be quite overwhelming in options and tutorials. My girlfriend likes Zelda, but hates traditional RPGs. Until she started playing this one, now she's hooked. Overall it's a good game, dated but fun, old school but not a boring levelling grindfest, hardcore but not elitist. DQ 5 and 6 are on their way, so this is a great place to start.