Others have addressed the point already, but I actually think the sales of the Wii version of Call of Duty: World at War compared to its HD counterparts only emphasizes the point I made about brand equity and product quality in relation to sales. To illustrate this, let's look at the Call of Duty franchise and its performance on the current generation of consoles.
Let's start with Call of Duty 3, the first Call of Duty made available on all current-generation consoles. Naturally, the 360 version sold best because of its larger install base and familiarity with the brand (Call of Duty 2). If we look at the PS3 and Wii versions, both of which were launch titles, we see that they sold at an equal pace, with the Wii version actually edging out the PS3 version by a slight margin. In terms of quality, however, Call of Duty 3 is considered across the board the worst iteration of the franchise yet. While the PS3 and 360 versions weren't amazing, the Wii version was a certified mess. It had sloppy controls, first-generation PS2 graphics and, worst of all, no multiplayer to speak of.
Next we arrive at Call of Duty 4. Now, Call of Duty 4 was, in every way, a vast improvement on its successor and an absolutely amazing game in its own right. The sheer quality and freshness of Modern Warfare propelled the game's sales to previously unheard of heights for the Call of Duty franchise, selling several million on both the PS3 and 360. The title skipped a Wii release, however, a mistake whose effects would be made clear later.
Finally, we arrive at Call of Duty: World at War. The game chose to return to its WWII roots and to again release across all three platforms, much like Call of Duty 3. Though not as successful as its modernized predecessor, the title still went on to become the second most successful iteration in the franchise. Partly because of the larger install bases, yes, but also because of Call of Duty's greatly improved brand equity.
Let's examine World at War on the HD systems. When PS3 and 360 owners saw World at War it was not Call of Duty 3's relative mediocrity that came to mind but the excellence of Modern Warfare, despite the fact that it shared both developer and setting with Call of Duty 3. The quality and recent familiarity of Call of Duty 4 ensured World at War's success on the HD front.
The same cannot be said of the Wii version. The only familiarity Wii owners had with the franchise was Call of Duty 3, a two year old shoddy hand-me-down, and perhaps the knowledge of the amazing Call of Duty 4 for PS3 and 360, a title Wii owners were not deemed worthy of. And while it was World at War for Wii was a decent game, it was still a significant downgrade from its HD counterparts that was failing to maximize the Wii's potential.
So rather than feeling fond memories of the excellent Modern Warfare, Wii owners felt only resentment at being left out yet again. It's no surprise that the sales of the PS3 version are tripling the Wii version of World at War, despite the equal performances of Call of Duty 3 across both consoles. It's simply a matter of quality and consistency.
The average Wii consumer may not research as extensively as us avid forum-goers, but it would be a mistake to assume that they would not remember being slighted. To me, it just shows that if World at War can sell as well as it did on Wii despite all of these enormous setbacks, then a market must clearly exist.