For me,
PS2 - I'll take Tyler
PS3 I'll take Lune
I do not think there are any in PS1 or PS4, really.
Now, in PS2, the only non-player characters I can think of would be Darum, Tiem, Tyler, and Lutz
In PS3, I don't count the "old" characters, like Old Rhys, etc...so your choices in PS3 are
Maia, Lune, and Alair
I just think Lune would really kick some azz in PS3...and Tyler would make things very interesting in PS2, I've written about this elsewhere...I really think Tyler should have joined your party in PS2. It would have made a far more interesting story, and a better storyline, generally. Plus, it would be a way to replace Nei, who you lose...so you'd have eight characters to pick your party from.
Tyler, being a Pirate, would, I believe have some very good strong attacks, and a few good techniques, too. He probably would not be much of a healer.
Even if Tyler didn't directly join your party...it would have been much cooler, in the storyline....if Tyler let you use his ship after he rescued you from Gaila...instead of this sudden appearance of a spaceship at the tower on Mota. And he could pilot the ship for you, taking you where you wanted to go, Dezo or Mota...and you could even talk to him at times to get more information about Mother Brain.
Tyler would be a very fun addition to PS2.



