Ohhh, you really need to replace those Boomerang pads! Even if you find some original Commodore ones, and just replace the D-pad in them. Hopefully we'll have comercially available PS2-CD32 adapters soon though.
Get Liberation: Captive 2, Microcosm, Fightin' Spirit, Ultimate Body Blows, Marvin's Marvelous Adventure, Banshee, Simon the Sorcerer, and those games already mentioned. There are plenty of great games that improve on the Amiga versions for the CD32.