They have lots of second party.  Halo, Viva Pinata, PGR, Forza, Gears, etc.

Most of the Nintendo games you are thinking of as first party are actually second party (Pokemon, Metroid, and many others).  

 Actually I could classify Viva Pinata as 1st party and most of the others as second party.  I think of second party as being made by an independent developer but that is published by the first party so Gears which is made by the multiplatform Epic (I think) is 2nd party though the game itself is only for xbox since its published by MS.  Viva Pinata is 1st because Rare is wholly owned by MS (though they are making one or two games for DS for some odd reason).

By that system, most of the Nintendo games are first party since Metroid/Pokemon are owned by Nintendo while some games like Zelda:Four Swords and the recent Starfox games are 2nd party since they were done by multiplatform distributors.  

I find that its easier to define parties using that definition. 

Rare is classified as a second party developer and their games are classified as second party games.  Similarly, Game Freak and Retro are second parties to Nintendo.  Whether you agree with that definition or not doesn't really matter because its the correct one.

@naz

If MS owns Rare, how are they second party? They are part of Microsoft.

Id consider Insomniac a second party b/c the make Sony games, but Sony doesn't own them.

Well Retro doesn't own the Metroid license and similarly has only made 3 games, the rest tend to be made in-house.

 The same way Retro is owned by Nintendo and is considered a second party.

Missing alot of 360 games. Lost Planet, NCAA football, Overlord, Two worlds, Fifa , Pro Evo soccer, The orange box, Lego Star wars.

Thank you. Comparing only the top 15 is quite limiting considering each 1 on the list is higher on the 360. Except, oh wait, Lost Planet is 4th on the list and omitted. It's also coming to the PS3.

Also, a lot of those games are also on the PS3, and porting to the PS3 or to the 360 from the PS3 (such as Burnout) is going to cost less than developing an entirely new game for the Wii.

A lot of you guys are telling Legend and others that they should consider the development costs, well you can also add all of the rest of the third party games and then count the PS3 versions as well.

Edit:  Oblivion isn't counted since the expansions have come out. 

Do you serve any purpose besides trolling?

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And I was going to comment that Lost Planet was left off the list but that observation has already been made.  And of course Gears of War misses out by being released two weeks before the Wii launched.

Go look at the North American charts for the top 30 games and count the number of third party 360 games and Wii games in that list. I counted 2 Wii games. If anyone actually thinks that the Wii is the bread and butter of third parties they're mistaken. I should take that last comment back, they are the bread and butter for third parties that release crap like Ninjabread Man. But for third parties that rely on hundreds of millions of dollars in revenue each year they're far from a sure thing.