The PSP has had an interesting life to say the least. It played second fiddle the Nintendo DS the entire generation in terms of sales. One might also argue overall its library wasn't as diverse. But when it came to the role playing genre, the Sony PSP had a library that rivaled any system any day, any generation. Whether it was brand new games, enhanced ports, imports the PSP was an RPG force. Let's get to it.
New Games
Final Fantasy VII: Crisis Core
A prequel to the PSone classic Final Fantasy VII, Crisis Core explored a different main character. One who died before the events of Final Fantasy VII even began. The gameplay is action based, you only ever do control one character. The Story is really just a nostalgia driven trip (not a bad thing). I think this should be a cornerstone of your library if you're a Final Fantasy fan.
Gungir
The latest in the Dept. Heaven series of SRPG's with a twist, this was a far more conventional SRPG. That didn't make it bad. The graphics on the PSP were beautiful and the character sprites are detailed. The story is very dark containing themes of death, slavery, and war. One of the last great psp localizations, its not a game to be missed.
Jeanne d'Arc
The first and only SRPG made by studio Level 5. The frightening part is even if they did make another, I am not sure they could top it. Everything about it was top notch. Mixing history with fantasy and using the location of France was brilliant because it allowed Level 5 to truly do something different than your standard SRPG. I also found the voice work particularly good.
Kingdom Hearts: Birth by Sleep
Officially Kingdom Hearts Zero, this title introduced us to not one, not two, but three main protagonists. In addition to gaining Kingdom Heart back-story, Square Enix introduced different scenarios based on the three main characters allowing the gamer to see the different perspectives
Phantasy Star Portable 2
This is the first Phantasy Star Online title that I truly got addicted to. I loved Phantasy Star I-IV so I was always a bit bitter that they radically changed the series as they did. I appreciated the multiplayer of this title as well as the deep character customization elements. It's a game I still play with friends because we can be in the same room and shout orders :P
The Legend of Heroes: Trails in the Sky
For the first time in any Generation we got Legend of Heroes games localized. While the Gagharv trilogy was butchered by Namco USA, the series got some new life via Xseed. While they promised to localize the VI trilogy, so far only the first game, Trails in the Sky, has been localized. Enough back story, onto why the game is essential. The game is an epic. A 60 hour epic. The world, characters, story are all so detailed its a feat of modern gaming. You might think I am blowing hot air, but that is simply the truth. The gameplay is a mix of strategy and classic turn base. Although the game ends on a major cliff hanger that resolves in the second chapter (unlocalized), that doesn't matter. It's worth playing on its own.
Valkyria Chronicles II
Sequel to one of the most beloved PS3 RPG's, nobody imagined the sequel would be on the PSP. While the scope of the SRPG battles are obviously smaller due to the hardware, Sega didn't rest on its laurels. They took the time to fine tune the gameplay and increase the customization options and character classes. The sequel also has far more missions (and mission variety) which adds to the enormous replay value.
Wild Arms XF
Wild Arms is one of my favorite Japanese RPG series, so even if the game is a side game, I take it. The game is an SRPG but it's not like any srpg you have ever played. For one, the battle doesnt take place on square spaces like most SRPGS but"Hex's" similar to the ones found in Wild Arms 4 and 5. Also, most SRPG missions fall into the trap of being nothing but "kill all the enemies". Wild Arms XF avoids that by having missions with a bit more variety.
Ys Seven
Ys is a series that has been around 25+ years and at its core has changed very little. Until this entry. The action rpg bump system which has made the series so famous is still there but its enhanced. For the first time you have a party of characters you can shift between offering different moves and strategies. When you're not controlling the party they are AI controlled. We can thank Xseed for the great localization work.
Z.H.P. Unlosing Ranger vs Darkdeath Evilman
The idea of crossing Disgaea with a rogue-like system almost seems like an invitation to be in assessable to only the most ardent rpg fans. Interestingly, not only is this one of the most accessible rogue-like on the PSP, it might just be my favorite. The story is so original. The main character gets hit by a car and you just happen to be passing by so you take over. I mean it's crazy. The graphics, humor, customization options are pure disgaea. Unfortunately many gamers missed this game when it first came out. Dont make the same mistake twice. Especially as a spiritual sequel is coming to the PS3 in the form of "The Guided Fate Paradox".
Ports
The PSP had some amazing enhanced ports. These 5 I feel are the best. Not only because the base games are already good, but they added either significant changes and/or new content.
Disgaea 2: Dark Hero Days
Final Fantasy Tactics: The War of the Lions
Growlanser: Wayfarer of Time
Shin Megami Tensei: Innocent Sin
Tactics Ogre: Let Us Cling Together