Give me your BEST MUST play games for PSX but on PSP

So a few weeks ago I've bought the PSP. I've installed ARK-4 CFW on it. I've downloaded some games and played them for those few weeks. I want you guys to recommend me the BEST MUST PLAY PSX games. Hidden gems games or just best games on your opinion. The library is so big and i have only 64gb sd card, so I can't put everything in one go. I want to play some of the games, then replace them with other games. Btw I want you to only recommend me the PSX games please.