When it comes to retrospectives, it's easy to let nostalgia blind us. What we consider to be a masterpiece could be someone's Worst Game Ever™.
Yet there's a cadre of games, given how massive the PS2's catalogue was, that make you instantly go "Oh yeah! I loved that game. Whatever happened to it?" and suddenly want to play it again.
There's always numerous factors as to why some games are one-and-done, in maybe it didn't score high enough critically or shift enough units. Conversely, it could be that they have had sequels, but it's the PS2 iteration we favour instead.
Psychic espionage, realistic war simulators, a traditional turn-based RPG with a difficult-to-pronounce name... they've all had some of their best outings on Sony's top selling consoles. Admittedly yes, they've been on other consoles too, but they qualify for this list through association and popularity.
The only downside to a nostalgic list is it makes you wonder what the hell happened so such a huge variety of franchises and game mechanics. Like why did a famously stealthy ninja game go all arcade-y and whack a Z on its name to look cool??