For people who are curious I present Tales of Legs.  All numbers from Enterbrain/Famitsu, and all mainline mothership games only... 

• Tales of Phantasia (SFC) 84,373 (228,738) 37%
• Tales of Destiny (PS) 450,099 (829,271) 54%
• Tales of Eternia (PS) 384,790 (669,248) 57%
• Tales of Destiny 2 (PS2) 498,142 (762,861) 65%
• Tales of Symphonia (GC) 183,527 (322,779) 57%
• Tales of Legendia* (PS2) 242,003 (343,332) 70% 
• Tales of Rebirth (PS2) 372,767 (596,493) 62%
• Tales of the Abyss (PS2) 368,316 (556,465) 66%
• Tales of Innocence* (DS) 106,733 (246,420) 43% 
• Tales of Vesperia (360) 101,272 (204,305) 50%
• Tales of Hearts (DS) 141,610 (261,751) 54%
• Tales of Graces (Wii) 143,309 (203,770) 71%

*developed outside Wolfteam / Telenet / Tales Studio, but still considered mothership releases

Can't attract the audience without the games.  ;)

Of course Graces Wii had some pretty big problems that extended beyond simply audience (it was unfinishably buggy, it launched in the wake of FFXIII)... I mean really, if it was just down to audience alone then there's no good reason for the game to have sold worse than the cheapo Symphonia spinoff did just a year earlier on the exact same system.  Honestly, I think had Graces been released at a different time (with no direct FFXIII competition) and without enough bugs to warrant mailed replacement discs (which killed it's legs), the game probably would've done 300k.  While that's still less than it's going to do on PS3, it'd be well more than it did sell with those issues.

Audience concerns (which *are* there) also are probably more specialized than just "JRPG audience", Tales games also sell better on DS than PSP, yet you never find anyone claiming a general JRPG audience problem there.  The "Tales audience" is on PlayStation certainly (and always has been imo), but that doesn't mean Nintendo (or Wii) doesn't have good representation with the general JRPG audience.