That's actually a tough one.
I don't judge myself as "hard to please" when it comes to games, so I could easily list the last 10 games I played as they all impressed me in one way or another. I should also state I'm in school as an upcoming game designer, so I learned to look at games as a whole but also break them down into parts, and to appreciate everything with a different eye then I once had.
The most recent "huge ass" impression left on me is WoW Cataclysm's 10 days trial. I hit level 20 in a day and a half of completely absorbed nonstop playing and had tons of fun doing so, and I had to force myself to not actually buy the whole thing at least until I finish this semester of school, otherwise I'm convinced I'd have been hard at it until I'd have hit level 85. For a game to capture me so completely so fast is unusual, even for me.
The most recent game I played was Recettear, which impressed me because it's another attempt at redefining the JRPG that is often said to be dead by looking at the genre from a completely different angle and still creating a very compelling gameplay. In fact, unlike the standard JRPG, Recettear focuses on its gameplay almost entirely, instead of telling a story over the gameplay, and the result is something that's genuinely fun. My reflexes I honed playing so many JRPGs in my youth (aka item hoarding and extensive exploratory grinding) are actually being challenged by the game, and it feels refreshing.