@ Reasonable
I agree with you. PSP games are often indistinguishable from PS2 games, which undermines the success of the handheld format. Indeed, most PSP exclusives end up on PS2 anyway, and I suspect that a great many PSP owners already own a PS2.
In contrast, the DS and the Wii offer exclusives titles that can only be experienced on their respective formats as a consequence of their unique controls. This is a significant advantage that Nintendo have over the opposition. Even the HD consoles are too much alike and clearly, this is the reason why many opt for either a Wii360 or PSWii combo as opposed to a PS360 combo.