1. Mario Kart U
2. Red Dead Revolution
3. Half Life 3

Runner Up's: Halo 5, Uncharted: The charted territory and Mario Universe. 

A good Final Fantasy, Hopefully Versus XIII
Kingdom Hearts 3
A new Dark or Demon Souls, on PS4

Hard to limit it to just 3.

From games I've seen at least a glimpse of and are coming soon:

1.Xenoblade 2
2.Watch_Dogs
3.Wind Waker HD

From games that are a little farther out and less known:

1.Zelda U
2.Mario U
3.Destiny

From what is announced...

Monolith Soft's X (Wii U)

Pikmin 3

Monster Hunter 4

Of course there are MANY more, but I had to make a choice :)

Uncharted 4
God of War 4
That new Guerilla Games IP.

inFamous: Second Son
Watch Dogs
Mario Kart U

Uncharted 4
Zelda WiiU
Pokemon U

new mario U
retros game
X

Not including games that have been already announced (where's the fun in that):

1) God of War IV - Egyptian Mythology reboot. This will be a huge system seller like GoW3 and with what SSM achieved with GoW2 on PS2 and their 1st PS3 game being one of the most acclaimed and still one of the best looking games this generation with its successor being the best looking game, I just can't wait to see what they do next generation. Hopefully they drop multiplayer and make the single player bigger and better than ever.

2) Mass Effect 4. 3) The Elder Scrolls VI. 4) Red Dead Redemption 2. 5) Bioshock ? 6) Gears of War 4/reboot. 7) Alan Wake 2. 8) Tomb Raider 2. 9) Deus Ex: ? 10) Fable IV. 11) PGR5. 12) LittleBigPlanet 3

- New IP from Sony Santa Monica. New IP from Guerrilla Games. New IP from Epic games. New IP from Media Molecule. New IP from Naughty Dog. New IP from Mercury Steam.

Sorry, I can't list just 3 games, I won't buy a next generation console before at least half of the above games have release. I really want a PS4 at launch but I'm going to resist, by the time the games I want are out it will probably have had a price cut anyway. I will probably get an Xbox One towards the end of the generation.

1. Uncharted 4
2. Watch dogs
3. Infamous second son
4. Witcher 3
5. Destiny
Sorry for adding two more.