Devil May Cry.
This year is imo by far the best ever for an individual platform. The PS2 had an insane amount of great games in 2001, some quite influential, some started sub-genres (DMC, ICO, GTA3), and some are of the biggest sellers of the generation (GTA3, GT3, FFX, and MGS2).
A few great games not mentioned here include Ring of Red, Klonoa 2, Maximo, Baldur's Gate Dark Alliance, Twisted Metal Black, Ace Combat 4, and Virtua Fighter 4. The "not mentioned" list alone can take on entire years!