I bought Monster Hunter Freedom Unite for the PSP, and had a fairly good time playing it, but then I bought Monster Hunter Tri for the Wii, and was slightly dissapointed. Maybe because it's mostly the same thing, like you have almost the same weapons and 90% of the enemies are just different coloured versions of the same four creatures.
Don't get me wrong, it's a great series, I just expected more of an improvement in a sequel.