Have there been any outside of Japan (which had MH3 and will have DQX)?  I've played some excellent 3rd party games, but not ones I can imagine people buying a Wii to play (it's not like they were even advertised!).  I suppose some people might have bought a Wii to play Just Dance, and maybe Epic Mickey and GoldenEye have sold the Wii to some people this Christmas, but other than that I'm really struggling to think of any - certainly not anything to compare to GTA, Metal Gear, Final Fantasy, Assassins Creed etc.  If there really haven't been any significant 3rd party titles that have significantly spiked Wii hardware (at least outside of Japan), that makes the Wii's incredible sales all the more remarkable.  It also begs a question of third parties who moan about their sales on the Wii - what have you delivered on the Wii that would make people want to buy one to play your game?

I'm sure Just Dance has sold more Wiis than most 3rd party games have sold HD consoles.

Just Dance 1 and Just Dance 2 may be big exceptions.

just dance and monster hunter definitely

possible Tales of Graces, as it was bundled with the Wii

I don't think Monster Hunter Tri was significant; it did boost the Wii about 100,000 units in Japan. The Wii was up 42% the week of Just Dance's release; but Just Dance didn't even make the top 50 that week, and New Super Mario Brothers had also launched that week to about 1 million sales.

Just Dance may not have had an instant impact, but true system sellers have a small, but long-term effect on sales...

I don't think there are many beyond JD and JD2. But does it matter? A third party doesn't care about pushing hardware, and Nintendo push hardware with their own system sellers. Third parties are supposed to round the library out (in the interest of selling their own games obv.), so there's a constant supply of moderate-big hits, but even that they couldn't manage on Wii.

Rather it is a weakness on the part of their competitors that they have to rely on external companies to provide system sellers (none of which have compared to the big Wii system sellers).

True (about Just Dance). It is fairly hard to see the effect other games have when Wii is home to many of the highest selling games in the history of the videogame industry; but they're first party.

There are 6 first party games on Wii that exceed 20 million in sales; and Wii Fit Plus will soon make it 7.

When a big third party really pulls out the stops and gets behind the marketing as well as the development of a game, those games often become titles that make people buy a machine in order to play it - GTA, MGS etc. fall into that category.  I can't think of any such games on the Wii outside of MH3 and DQX.  Third parties often complain about the Wii audience not responding to their (often very poorly marketed and often quite mediocre) titles - my point is that genuinely big titles reach beyond a system's existing audience and present non-owners with an incentive to buy the machine.  I don't think third parties have done that with their Wii titles - instead, they have focused very narrowly on what they perceive the Wii audience to be, and in so doing aim at a market created almost solely by Nintendo.  This being their method, I don't think it's such a surprise that so many third party titles fail when they are almost always inferior (often enormously so) to and less well marketed than Nintendo's own titles.