For PS2, that would be Rule of Rose, the .hack series, Shadow Hearts, Suikoden V, and Wild Arms Alter Code F. Xbox would be the Steel Medalion Set with the Flight Stick Controller, GTA Trilogy, The Guy Game, and Halo Triple Pack.
For both systems, Jurassic Park Operation Genesis, Digimon Rumble Arena 2, and Marvel Vs. Capcom 2.
Honestly, most of the U.S. releases aren't too pricey, especially for PS2 so they're fairly easy to get and you may to able to find decent prices for most of these if you look hard.
Imports on the other hand, especially the Japanese PS2 shooters, are quite rare and expensive to acquire, especially Ibara.