Hmm, I'll do it by console:
Most Pleasing
PS3: Ace Combat: Assault Horizon, just got it the other day and I am LOVING it, the soundtrack is great, controls are awesome, and once you chuck it into the cockpit view the immersion skyrockets. A very close 2nd goes to Catherine, love the story, characters and gameplay...yet to finish it.
PSP: Kingdom Hearts: Birth by Sleep, it was SO nice to get some backstory on the KH universe altogether, and they actually did the 3 stories so well, it blended fluently and answered a lot of questions while not sacrificing combat. Close 2nd to the 3rd Birthday, best shooter on the PSP with lots of twists and just overall great.
Most Disappointing
PS3: Atelier Rorona, I tried so SO hard to like this game; I've played Mana Khemia and all three Atelier Iris games and love them to death and I could not stick with this one. The combat was the main clincher, since you could barely do anything with the characters you started off with, and that skills used HP, I love the guys who created the game, I love the series altogether, but I could not like Atelier Rorona.
PSP: Holy Invasion of Privacy Badman! I like this game, the humour and such, but the gameplay is weird, and I haven't stcuk with it long enough to get used to the difficulty and style of gameplay, so I really need to give it another shot. I love all my PSP games, but this is the most 'disappointing'.