I like JRPGs and WRPGs almost equally. I haven't played a lot JRPGs, but the ones I played mostly differed from WRPGs in the following areas:
- The visual aspect, obviously
- The way skills was handled. The games had no/few skills outside combat, so skills like Lock-picking, Sneak, Charisma seem rare in JRPGs
- None/few of the games had interactive dialog
- Few quests with multiple solutions, partly because of the less focus on skills outside combat
I understand why some people don't like these aspects of JRPGs, but if the world is interactive enough, the story and characters interesting, and I like the combat system, I personally don't mind (I'll come back to the visual aspect). The design philosophy is probably to sacrifice multiple approaches and parts of the character development to keep the plot and characterization stronger, and interwoven.
The main reason I personally like this sub-genre is because of the different approach to setting and the over-the-topness. Especially the enemy design tend to be very charming and creative. I'm not that much into games with the typical/clichéd anime inspired humans/human-like characters, so I tend to avoid those games. IMO, far too many WRPGs are based on more or less the same Medieval inspired setting and enemies. The western sci-fi ones come in more shapes and colors, but still feel a bit samey after a while, IMO, and are unfortunately a bit less common than western fantasy RPGs. So after I've played one or two western fantasy RPGs I'm a bit sick of "realistic" environments, orcs, dragons, brown and grey - or similar traits and features. Then I either turn to a western sci-fi RPG or a JRPG to mix things up a bit.
But actually a lot has happened the past 5-6 years, and nowadays a lot of JRPGs have action-based combat, at least to a degree, but AFAIK in most of them the combat takes place on a different map, and my guess is that it turns some people off.
EDIT: Clarified a few things.