Even as someone who thinks most of Sony's first party output isn't great, it's a no contest. The PS2 just had SO MUCH great shit that never went anywhere else. Disaster Report and Raw Danger, the Maximo games, the Fresh Games releases, God Hand, all those SMT releases, Bujingai, Drakengard, the Simple 2000 series, Tokobot, Jade Cocoon 2, Dragons Quarter, Digimon World Data Squad, Magic Pengal, Chulip, the fucking ATHF golf combat game, the only good Transformers game in history to that point, Musashi, We <3 Katamari, mother fucking Death By Degrees!
This is not even counting imports, or ANY of the major stuff. You can name drop 100 PS2 games and still be naming incredibly unique, special games, and you'd also be just cracking the surface of the library, whereas you'd be hitting the bottom of the barrel on the rest with exclusives. And I love those other libraries! I have more games on Xbox and GameCube than I do on PS2, but they absolutely do not come close, not even counting on my natural bias to lean towards both Xbox/Nintendo over Sony.