Kingdom Hearts Birth By Sleep (but we're probably going to get a Birth By Sleep 2 or something judging by the secret ending in the Final Mix)
Crisis Core -Final Fantasy VII- (doubt I would be willing to rebuy it though)
PHANTASY STAR PORTABLE 2!!! (I understand PSO2 is coming out for the Vita and all, but still...)
Metal Gear Solid: Peace Walker (I was astonished this was not on the list.)
Final Fantasy Type-0 (I would rather want an HD release or a Vita optomized version though)
Star Wars Battlefront: Elite Squardon (Kinda surprised that got the axe too)
Resistance: Retribution (Although with Burning Skies announced there isn't much of a point in releasing it)
Final Fantasy I and II (This was kinda odd not seeing on the list. Didn't bother me though since I have the PS1 Origin game, which could be why they took those two down)
Patapon 3 (Why is only Patapon 2 up there?)
Secret Agent Clank (They got Daxter up there I don't see why they don't have this one)
Star Ocean games (See MGS: PW)
Valkyria Chronicles II (Really!? What is Sony thinking at this point!)
Digimon World: Re:Digitize (Well, I can't say this hasn't been added or not and there's not even a NA announcement yet and I don't expect one due to Namco killing off it's US branch pretty much. Although, I wish it was for the Vita instead)
Yet, out of all the ~750 PSP games out there, only ~275 are added (the list is old and they lied when they said they would update the blog post with new games) and most of those games are not worth it. Prime example: Cloudy With a Chance of Meatballs (released in 2009) is $30 USD. Corpse Party (released in late 2011) is $20.
EDIT: I'm not saying Corpse Party isn't worth it, but showing it's great and has a low price compared to Cloudy which is mediocre quality and a higher price. And older.