For me?
Mirrors Edge - Xbox 360. When I first heard about Mirror's Edge, I'd been spending my time watching parkour videos on youtube, and I was really excited. When I got it, I ran through it in about 2 days (After a period of trying to learn the controls well enough to play it) and to this day, I still enjoy it.
Project: Snowblind - Multiple systems. Most people don't know this game exists, and honestly, it was a small release from Eidos and Crystal Dynamics, and went relatively un-noticed, save for the fact that many people thought of it as a Non-RPG Deus Ex. But, I still like to lace up Lt. Nathan Frost's boots every now and then, and give it a good run through.
Sony Playstation All-stars Battle Royal - PS3 most people heard about this game. Most people dismissed it as a Super Smash Brothers ripoff. Maybe so, even I did at first. But having finally played it, I really like it. all of the characters have a unique play style (Although some are broken, some suck, and some DON'T BELONG THERE. I'M LOOKING AT YOU FAT PRINCESS.) and there is enough customization to make you pop it in from time to time, alone or with friends. Not to mention, it was Sir Daniel Fortesque's (Medievil) first appearance since 2006, Sly Cooper's first new game in about the same amount of time, and the first time I'd seen Parappa the Rappa in a long time. Although, the game always spawns the same discussion when I play it with my friends. WHERE IS CRASH AND SPYRO?
Alpha Protocol - I think it's on both 360 and PS3... o_O. I used to talk a lot of trash about this game, but I recently realize how much I like it, and why I was so furious at it. When it was announced, it sounded awesome. I was really excited to play it. I wanted to be so good. I was let down. for what it was, it wasn't bad. but for what was promised? it sucks.