The problem with genres is that after a certain amount of time, there will be so much bleed as to make them mostly useless. Everyone from Kanye West to Korn gets called Rock from time to time, there are 62.5 million sub genres of metal, some which get really anal retentive, and what the Hell isn't pop these days?
RPGs were easy to define once upon a time, even though they weren't always strictly quite games where you adopted a role. But then everybody and their momma broke out with "RPG elements," to the point that there are few genres that don't borrow some from RPGs.
JRPGs, at least the ones we get over here, have gone far less toward the RP part than their predecessors (And many of them seem to be dropping the G as well). But since that includes titles like Final Fantasy, it's hard to really re-label them. And even still, the ones that play on rails still offer a lot that is common to RPGs. Leveling, large world (though not as immersive), exploration and looting, etc.
"RPG" Tells me about half of what I need to know. It's not a comprehensive description, but it tells me there's elements I'm likely to like. Anything else should come down to game description. No genre will do a good job at covering all its bases, as even JRPGs occasionally have something other than femmey boys in shiny armour with big swords.
Even if we drop the RPG entirely, you end up in a ridiculous scenario. Is it a Tactical, Turn-Based, Action-Adventure Assumed Persona title, or does that ticking bar make it technically a RT? Or maybe we need a third hybrid option. Is it tactical, or does the ability to hold down the X button to repeat your moves ad nauseum remove the T? Are the platforming scenes enough to really mark it as an action game?
Genres work to describe levels of commonality. If you want more, you're better off going with a real description, because by the time you've finished your acronym, you're probably going to have one anyway. TTB/RTHAAAPSPPWSJPB...That gave me a migraine looking over.
