I have no sources, but the big determination and stereotype that I associate with JRPG's is the overdramtization, or when they exaggerate the same generic angsty character.
Devs in Japan definitely take the less realistic route with their video games, and exploits the paranormal and fantasy more so than the American Developer (or Western Developer would probably be more appropriate). We are more likely to embrace... I guess masculinity, whereas the Japanese side is more willing to allow their viewers to embrace a much more an immature(not to be taken as an insult) character and story arc. Westerners embrace much more dark and dangerous themes. Hell, War, Corruption. Japanese often have more light fantasy, school themes, and mellow themes in general.
I guess my source is to look at how popular Metal Gear Solid is over here, which blends the elements of both cultures fairly well. You see the overdramatization, while at the same time you see the masculine, matured, and gruff protagonist. Also, another thing that points to that is how a good amount of the Western fanbase hated MGS2, which featured an annoyingly immature character that people despised, only to be brought back into the series as a more likable gruff and battlehardened warrior.