Suikoden - Heard great things but never got around to trying em so can't say
MGS - I would say it didn't age great but it's playable
PE - I've been meaning to play third Birthday, but PE 1 and 2 I use to love as a kid. Oddly enough I'm not a fan of the type of game so that says alot.
Castlevania - I can't help with
P2 - I personally don't like any before 3, but it's mainly because 3 and 4 kinda pulled away from SMT and made it seem more like it's own thing. I actually dislike anything SMT that's not Persona 3 and up lol. Though the FExSMT looks interesting
Disgaea 2 - All Disgaea's are similar it all plays pretty similar, if you like disgaea you'll like this. They age as good as tactics style games could
VC2 - Love that game, it's a good addition to the series though it's still odd it came out on PSP and not PS3 lol
Lunar: Silver Star Harmony - Actually surprised you didn't hear of it. This game is one of the biggest surprise releases for PSP to me. Notperfect but the game is hands down amazing. It's a rerelease of a game on Sega CD and PSOne I believe. Definitely the best version. I highly recommend.
Ys - Depends what you want, Ys Seven is the one that is pretty similar to Ys Celceta and Ys 8's battle systems. Ys 1+2 is really a classic game if I remember correctly, fights were like bumber cars and you can just hope you are strong enough to kill everyone. Hard to explain, I'm sure I'm making it sound bad. Oath is good if you like other newer Ys but want something different.
Oreshika - Skipped because I don't trust taking the chance on it. and it's Digital only so I said screw it. I can't say if it's worth your money. Should Check a review maybe or some gameplay impressions