Because every single game follows the same basic formula and the only thing that ever really changes are names and haircuts?!?
To me Tales of Eternia (Destiny II for PSX in the US) was the only one that stood out, though it's still familiar territory if you've played any other game in the series. I've heard that Tales of the Abyss stood out as well but I haven't played it myself (lost my PS2 before I was ever interested enough to try the game out.
I hear Tales of Legendia stood out as well. Apparently a lot of Tales fanboys hated it, maybe it's good then. I've read the plot premise and seen the character designs and it does look pretty different from usual Tales stuff.
By the way, I recommend Final Fantasy Tactics War of the Lions due to good gameplay (hate those pseudo-random battles from which you can't escape though!), great plot (much better than anything you'll ever find in Tales) and beautiful cel-shaded, storybook-esque cutscenes!
Lost Odyssey is also good but it doesn't really add anything new to the genre. Most characters dress ridiculously, there's some slight slowdown on some parts and the plot and world could've been better. The world felt really empty when compared to what Kaim's memories (short stories presented in a visual novel fashion which describe memories from Kaim's past which he remembers along the game) described. To me the memory segments were definitely the game's highlight plot-wise, I just wish the guy who wrote those short stories could've written the game's plot as well. The game also has some excellent music (especially during the memory segments) although there ares some tracks that I just can't listen to.