Pretty straightforward. Going by whatever criteria you wish (sales, significance, hype, epicness, your own anticipation), list what you think will be the biggest game for each of the 5 (or 6 if you want to include PC) platforms this year.

To start, i'll go by overall significance (something that will be the best remembered, not necessarily sell most)

1. Wii: Zelda Wii. Iwata said it today, but i think this game will be the holy grail for motion-controlled gaming, the game that makes all of the skeptics say "I get this." An engagement like no other.
2. Xbox 360: Fable III. It's a bit of a stretch on my part to predict it will arrive this year, but if it does, it will do for 360 what Zelda Wii does for Wii, and be a smashing inauguration of the 360's oncoming motion controls.
3. PlayStation 3: Gran Turismo 5. This is the game that will fulfill the PS3, the one owners have been waiting for. Jaw-dropping holy shit HD quality.
4. Nintendo DS: Miyamoto Social Project. This one's a little woolier, as we really don't know what's in the pipe, but there was recently a story that Miyamoto was working on a "social" game for the DS, which could be something like the next Nintendogs, and fire the imaginations of the world accordingly
5. PlayStation Portable: Kingdom Hearts: Birth by Sleep. The year for PSP isn't known so much either, but this game really looks like a winner, a full-scale, epic engagement on the go.
6. PC: Starcraft II. Need i explain it?

What do you think is going to be huge in 2010?

Wii -- New Super Mario Bros Wii

yes it will continue to sell & cross 20 million....so will see 12 million in 2010

PS3 -- Gran Turismo 5 & Final Fantasy XIII

no explanation required

360 -- Halo Reach

I will actually predict that Metroid: The other M will be the biggest "OMFG" moment on the Wii.
The new Halo on the 360.

I agree with you on the rest.

The overal would probably be Starcraft 2.

Quality-wise?

Wii - Zelda Wii (Full use of WM+, and it's Zelda!)
360 - Mass Effect 2 (The first was epic, and the 2nd is just extending and improving everything!)
PS3 - Gran Turismo 5 (Just look at all the features this damn game has! Not to mention the new physics engine is awesome too)
DS - No idea.
PSP - No idea.
PC - StarCraft 2 (Obvious reasons)

Halo Reach, GT5, Wii Relax or Zelda Wii, I have no idea for DS or PSP.

1. PS3 - GT5, its been a while and the specs just shows how huge this game will change sim racers. GoW3 should also get a honorable mention here, that game definitly compares to Uncharted graphics wise.
2. 360 - Halo Reach, its Halo and it will be entirely newplus its the last halo game, so ya.
3. Wii - Zelda

Wii- New Zelda-Doesn't even need a reason.

360- Halo:Reach-For Story and online.

PS3- God of War III-For Story and Gameplay, MAG for 256 player online...yeah.

DS- Pokemon HeartGold and SoulSilver-You can't say you have never picked a Pokemon game up, and if you have then you know how great they are.

PSP- Metal Gear Solid: Peace Walker-MGS game...again doesn't need a reason.

In terms of my own anticipation:

360- Halo Reach

PS3- God of War 3

Wii- SMG 2

PSP- MGS: Peace Walker

DS- DQ IX

Miyamoto social game?

Facebook 2?

StarCraft II is going to be so big I'm actually going to become 15 years old again when I play it.

Wii: New SMB Wii will probably be the biggest seller, unless some crazy Wii Vitality thing creates another revolution like Wii Sports and Wii Fit did. Critically, everybody will cry over Zelda and shit their pants over Metroid.

PS3: GT5. It will be be the PS3's best-selling game ever.

360: Sales-wise... I'm guessing Halo Reach. Critically, I'm guessing Fable 3.

I haven't been paying much attention to the portables for 2010. I just kinda figured the DS would sell about 8290375029 billion systems and have a ton of amazing hits as usual. Don't know much about the PSP's future.