It's not rare to see games ported across the PS2, the PSP, the Xbox, the Xbox 360, and the GameCube. This is excellent for the overall health of its release calendar, but potentially boring for gamers who are looking for a more diverse experience. When a developer does come up with an "original" PSP game, it's often a spin-off of a popular console series with heavily reused assets (Liberty City, Burnout, Katamari).
It's not as if the DS is faring much better. Yes, third parties are in love with the little odd-shaped-portable-that-could in Japan. But in the U.S., the DS is seen as more like the successor to the Game Boy. Far from the brief flirtation with adult games like Sprung, Western devs are looking at the DS and thinking, "kids." But then again, considering how big a business the cartoon-licenses-on-GBA racket is -- and that Nintendo sold nearly 5 million GBA units in the U.S. last year -- the DS is in an excellent position to take that market home in 2006.