Blew me away, as in I was very impressed by the game and perhaps did not think it would be that good, I will give examples of some of the first games that comes to my mind.
Shadow of the Colossus(PS2). I had not played ICO before SotC and did not know much of this game. All I knew was that it's a game from a pretty small studio and the game looked interesting. But surely this game really "blew me away". Really loved it. And while I played ICO after SotC it didn't blow me away or anything. If I had played ICO before SotC the tables could have been turned, most likely.
Uncharted 1(PS3). Surely this studio had a lot of years on it's history, and some already famous franchises like Crash and Jak. But Uncharted really gave me a great experience. And while I enjoy Uncharted 2, 3 and The Last of Us more than Uncharted 1, with the other three games I more or less expected to be "blown away", so I wasn't. I just got what I expected more or less.
Zelda: Ocarina of Time(N64). While I really enjoyed the other previous Zelda games this first step into the 3D-world and the great story really blew me away. Such a great game and pretty much still one my favourite games of all time.
Banjo Kazooie(N64). Did not know much about this studio and then this game popped up. Didn't expect anything from it but it was so good. And while I enjoy Banjo Tooie more, I expected it to be better, so it didn't blow me away or anything.
Battlefield 2(PC). While I had plated BF 1942 but didn't like it too much really, it was good but not great in my opinion, this game(BF2) really surprised me how great it was when it came. Such an awesome game until the latest updates where they removed some of the best, as they described them, bugs. The ability to duck and shoot fast and then get up again.
Battlefield 3(PC). Since I thought that BF 2124 really sucked in comparison to BF2, this game once again blew me away. I thought that the online multiplayer kind of sucked, or at best was average, but the single player campaign was awesome. Truly awesome.
And there are a lot of other games that blew me away, but I kind of expected them to be great. As Resident Evil 4, I expected it to be a great game. Perhaps I didn't expect it to be the best in the series ever kind of great, but still great. And same goes with Metal Gear Solid 4.
Zelda: Minish Cap(GBA). I didn't expect it to be as good as it actually was. I didn't enjoy Capcom's previous Zelda's this much so yeah this game kind of blew me away too.
In the Next Gen/Current Gen(Wii U, PS4, X1)-era, nothing has blown me away as of yet.
Good list. I played them all, except Battlefield. I especially agree with Minish Cap. I restartrd that game several times for months. Just couldn't get into it and figured it would suck. I stuck with it eventually and it just clicked. For the next several days, nothing else mattered. Totally didn't expect it to be one of my favorite games that year.