Hmm. Let me see. The ones that really wowed me, huh... ? I will only count games that, to me, brought something new to the table. So for example, I love Twilight Princess to death and think it's the third best game of all time, but it didn't really wow me in a way that previous Zeldas had not (except visually), so therefore it will not be on the list.
1. Super Mario All-Stars - What got me into games to begin with. It's hard to deny how great this gem was.
2. Super Mario World - Took everything I loved and perfected it. It was fantastic.
3. The Legend of Zelda: A Link to the Past & Super Metroid - Taught me that games don't have to be Mario to be awesome. Started them up and played through them too many times to even count, and I still do from time to time. Truly spectacular games.
4. Super Mario 64 - Brought me into a whole new world of experiences, and is, to me, the best game ever made. Truly showed me what 3D was all about (even though I'd played several 3D games on PC before I touched Mario 64).
5. Starcraft - Might well be my most-played game of all time, and pretty much the only game that bound me to PC for so long. The epitome of RTS, and still is better than it's successors in my opinion. Hoping Starcraft II will improve on this massive win of a game.
6. Metroid Prime - What really brought me into last generation was the revival of Samus. Put the Metroid-series into an entirely new perspective and just wowed me at every turn.
7. The Legend of Zelda: Wind Waker - Took the Zelda-formula and put it into a massive overworld with a perfect graphical style that's never going to age. Sure, I prefer realism in Zelda, but Wind Waker is never going to get old simply because it can't look much better than it already does. Only different.
8. Resident Evil 4: Wii Edition - Without a doubt one of the best games ever made, made even better on the Wii due to the Wiimote functionality and the added features from the PS2 version. I've only played through it once but I remember it fondly. The atmosphere, the gameplay, the dialogue, the enemies... It was all just fantastic.
9. Tales of Symphonia - Played it way later than it's release because a friend convinced me to, and it was spectacular. I had been a fan of JRPGs for quite some time, but this one showed me just what a JRPG could be, gameplaywise. Not just turn-based clicking, but actually taking part in the action - and along with a friend. Opened my eyes to the Tales-series, something I will never forget.
10. Metal Gear Solid 3: Subsistence - Played this game later than it's release as well, but it showed me the cinematic effect that a game could bring to you. Sure, I'd played games that were heavily cinematic before (MGS, MGS2, FF-games), but MGS3 really gave me something different. See my MGS3-thread for more clarification.
11. Super Smash Bros. Brawl - I've never been as hyped for a game as I was for Super Smash Bros. Brawl. And it delivered on every front. Fantastic local multiplayer and a cast that makes me explode with nostalgia. Well-balanced characters, spectacular graphics and just overall one of the most polished games I've ever had the joy of playing. I will never forget it.
12. New Super Mario Bros. Wii - This game didn't do that much new(though 4-player multiplayer is superb), and it didn't reinvigorate gaming for me... But it did something even greater. I have periods of pretty serious depression, and during my latest one which had been going on for a few days, I invited four friends over. We chatted, and then when we decided to do something we hooked up the Wii and started NSMBWii. I had already completed the game, so I let the four of them enjoy it together. And just watching the screen, and watching them, within 10 minutes my depression was all gone. Sure, it'll probably be back several times during my life, but I won't forget that moment where it just magically disappeared.
So there you have it.
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