Form what I've heared the Spyro games after 3 are not as good, as they weren't made by Insomniac (the developer and creator), but Universal. Same goes for Crash Bandicoot, though I did enjoy Wrath of Cortex and Twinsanity.
Another game I forgot to mention was Wild Arms, a western styled RPG, another underrated one from what I hear. You're so lucky you can get Chrono Cross. In Europe they're nowhere, as there was no PAL version :/ I'm relying on an emulator now, but if someone has any information if PSX games are region locked on the PS2 I'll gladly look for the legit disc.
If you have a gamecube or a PS3, you probably can get the Metal Gear Solid 1 remake (for the GC) or the HD collection (1 2 and 3 with bonus missions).
Also it seems funny that you talk about how Megaman X6 strayed from the formula, seen as MMX1 was quite different from MM1 altogether. From what I've heared X4 wasn't bad (X7 was really the one people didn't like)
As far as I know Disgaea (Tactical RPG) came out for PS2 not PSX. But another Tactical RPG for PSX is Final Fantasy Tactics. Game tells a story of two kingdoms fighting for control of the land and two people who carved the future of those 2 kingdoms. If you ever played Final Fantasy Tactics Advance/FFTA2 then it's pretty similar, yet still quite different.
The game got a remake called War of the Lions for PSP and iOS with additional cutscenes, characters etc. If you want the PSP version, beware. The game lags royally when doing any techniques. This is fixed in the iOS verison, but you can play normally on the PSP if you install a patch (but that's the PSP version, not PSX. PSX is perfectly fine).
Another game: Tony Hawk's Pro Skater 1-4. It's a skating game, pretty well known so I won't talk for much. However I heared that the newer ones have more tricks etc. Not that it matters if you never played one.
If it wasn't obvious: Tekken as a fighting game. Also Bloody Roar 2 is a fighting game, pretty all-right.
Geez another wall of text >.>







