This is not a list on gametrailers. I'm making this list myself. And I'm trying not to base it on my preferences, but on how I feel how far that game's impact goes.

10. Wii Sports
Killer app for: Wii, motion controllers.
Some would say this is just a tech demo. I say so the hell what? For a tech demo, it works pretty damn well. And in case one would comment it's just a pack-in, note that it's the top selling Wii game in Japan, where it isn't packed in.
Why it's #10: It's still too soon to see the full effect of this game.

9. Sonic the Hedgehog 1
Killer app for: Mega Drive/Genesis, platforming games that broke the Mario Mold.
For one brief, shining console generation, Sega was a heavy hitter, and it started largely thanks to this game.
Why it's #9: The game couldn't stop Sega from screwing themselves over.

8. Tie: Grand Theft Auto III/The Sims 1
Killer app for: The PS2, but mainly the do whatever the hell you want games.
Sure GTA III ensured the dominance of the PS2 (the GC and Xbox could have gained some ground, if not for this game), but that game and The Sims showed that games didn't have to follow a linear path, with the occasional side mission or bonus round.
Why they're #8: For one thing, Sony got real cocky after the PS2. For another, the sandbox genre still consists largely of Sims and GTA clones (Animal Crossing and Elder Scrolls being notable exceptions).

7. Goldeneye
Killer app for: N64, console FPS, multiplayer games.
There's a reason Halo 1 and 2 aren't in this top ten, and Goldeneye is it. For one thing, it helped the N64 regain its footing after the developer exodus. For another, it showed that FPS on a console is possible, although not as smooth as on a PC. Finally, the game was one of the first ones to sell largely thanks to its multiplayer (along with Mario Kart 64), paving the way for games like Mario Party, Super Smash Bros, and of course Halo.
Why it's #7: 1. It only stopped the N64 from loosing more ground, not regain any lost ground, and online FPS multiplayer was already big on the PC.

6. Tie: Nintendogs/Brain Age
Killer app for: The DS, and the resurgence of the importance of casual gamers.
Edutainment games and pet simulators becoming blockbuster hits is shocking enough, but enough to counter the threat of the Playstation (and the PSP was a threat, or else Nintendo would have not rushed the DS), AND ensure that Nintendo would actually not worry about rushing out the almighty Pokemon? That's just insane.
Why they're #6: Like Wii Sprots, it's still too soon to see their full effect.

5. Pokemon
Killer app for: Gamboy (after Tetris), Gameboy Color, AND Gameboy Advance.
A good killer app can secure a system's fortune for one generation. The Pokemon games secured three of them. Plus this shows that you can call Nintendo a kiddie company all you want, but like Disney and J.K. Rowling, they are too busy counting their money to give a sh*t.
Why it's #5: Well it's not as though the Gameboy line had that much competition. Even the Game Gear was out before Pokemon came out.

4. Final Fantasy VII
Killer app for: The Playstation brand, CD gaming, and RPGs in the west.
Nintendo seemed to have a good argument for carts, until this game came along, and showed a massive presentation, that was not possible with carts (and the DS can only do it now thanks to compression possible today). For those thinking CDs were only good for games like Myst, this showed they could make full games. And what it did to the Playsation, and RPGs in the US, need no further mention. It's already obvious.
Why it's #4:I just think the top 3 did a little more, and it's my list.

3. Super Mario Bros
Killer app for: NES, and reviving gaming in the US.
If I have to give any more details, you just don't know that much about gaming history.
Why it's #3: See #4.

Tie: 2. Virtua Fighter 1/Super Mario 64
Killer app for: N64, but more importantly, 3D gaming
VF1 may not have been the first 3D polygon game, but in a killer app, it's not who does it first, it's who makes it work first. And developers were not that hot on 3D gaming until they saw this game, and realized they could create an entire virtual world. Mario 64 sealed the deal for any naysayers.
Why they're #2: Well 2D gaming isn't dead, for example Brain Age is largely a 2D game.

1. Tetris (Gameboy version)
Killer app for: Gameboy, but also EVERY handheld game since then.
Of course true handheld gaming was more thanks to the development of dot matrix LCDs (since the Lynx
came out the same year), and the importance of battery life was set in the Gameboy's hardware, the rules of a successful handheld game were set in stone by this game, even if it wasn't designed for the Gameboy.

Play sessions should be designed for anywhere from five minutes to five hours. Assume five minutes will be the maximum for players (at least when saving became more prevalent). Make the game easy to get into. And make the game easy on the eyes (especially with the screen as it was on the Gameboy). Now look at every handheld game since then, and note how many followed those rules. Most of them do, even if the system didn't succeed. And it was thanks to Tetris.
That's why the Gameboy version of Tetris is my #1 VG killer app.

i say move SMB to #1 and FF7 to #2 and then bump everything accordingly IMO....still a decent list, this is super tough to do, also, as we have been blessed with so many great games over the ages......personal tastes are too tough to keep out but i think you did a pretty good job.

No Gran Turismo, list is mehh!

 GT was a great seller, but that isn't the same as a killer app. GT1 came out in 1998, well after the PS1 was secured as the top system.

Super Mario Bros 3 should be there not the first one. SMB1 set the ground work for 3, and is far from superior to it. To this day it has made greatest games of all time lists consistently if not at the very top. GT 3 came with the console where I am, and I did play that. It was very fun but sure ain't one of the greatest of all time. The others I never played though.

 Like Gran Turismo, Mario Bros 3 was out when the system was already a hit. Do you know what a killer app is?

 thats pretty much WHY it belong actually

No Super Mario 64. Hell that was the killer ap on the N64 to end all others. Not to mention hands down the greatest launch gam ever.

#2

I would argue Sonic 2 was bigger than Sonic 1. I never even played Sonic 1 until I bought Mega Collection for my Cube. Sonic 2 introduced elements such as the spin dash, multiple protagonists, and the Chaos Emeralds/Super Sonic. But this is my opinion... I've been told Sonic 1 was a much bigger game than I believe before.