I.e., can the top 8 Wii U games (I could only find info for the top 8 Wii U games) outsell the top 8 GameCube games?

GameCube has 35.57 million across the top 8 and Wii U has 27.67 (as of March 31, 2015).

Here's the sales of the games for

1. Super Smash Bros. Melee - 7.41 million

2. Mario Kart: Double Dash - 6.88 million

3. Super Mario Sunshine - 5.91 million

4. The Legend of Zelda: The Wind Waker: 4.43 million

5. Luigi's Mansion - 3.32 million

6. Metroid Prime - 2.75 million

7. Mario Party 4 - 2.46 million

8. Pokémon Colesseum - 2.41 million

Wii U:

1. Mario Kart 8 - 5.11 million

2. New Super Mario Bros. U - 4.81 million

3. Nintendo Land - 4.68 million

4. Super Mario 3D World - 4.10 million

5. Super Smash Bros. for Wii U - 3.65 million

6. New Super Luigi U - 2.25 million

7. Wii Party U - 1.55 million

8. The Legend of Zelda: The Wind Waker HD - 1.52 million

Obviously we should keep in mind that new Wii U games are going to come out that could get into the top 8 (Splatoon and Zelda U are good examples), and that none of the Wii U games are done selling.

I'm going to say that they will. Each of the top 8 Wii U games would have to sell a little more than 4.4 million to pass up the GameCube's games. I seriously doubt that will happen, but games like Nintendo Land, 3D World, Mario Kart 8, NSMBU, and Smash Bros. will compensate for the lower sales of the number 6, 7, and 8 games. Assuming every game in the Top 5 sold as much as Mario Kart 8 (5.11 million) lifetime, the top 5 would total to 25.55 million, meaning that the last 3 games would have to average 3.34 million sales each. And the top 5 games are all likely to sell past 5.11 million (MK8 already has considering this data is from 3 months ago), which will lower the required average for the last 3 games even more (So meeting the required average wouldn't be much of a problem for Zelda U, Splatoon, and Luigi U. But it should be pretty close.

Why are just doing the top 8? That seems like a pretty random number.

 I couldn't find official Nintendo numbers for Wii U games past the 8 highest selling ones.

Oh, okay. I think that it's possible, though that would mean that the middle games will be much lower than on the GC.

I get a feeling the Wii u will come out on top for this. Mario Kart 8 is going to outsell melee imo and Splatoon is soon going to be here when more updates come and will surely be in the top 8 and help bring the Wii u up. Mario Maker is also going to be a big seller and should be in the top 8 to boost the Wii u even more.

hmm, that's an interesting question. The Wii U's top 8 need about 8m more to pass the GC's top 8. And I don't expect Zelda U to sell more than 3m, or MK8 to pass 7m, or Splatoon to reach 3m, so given that, I don't think the Wii U's games will outsell the GC's.

Wii U top 8 can overthrow that GC top 8. Zelda U and Splatoon to replace WIi U Party and WW:HD. and MK8 and Smash would still get those good numbers. it would be close though.

I think it can,

the others I agree with though.

Hard to say.. it's possible, but I don't really think so

What was the game most bundled with the GC? Did it have a "Nintendoland" that probably would not have done nearly as well on its own?