Besides Wii Music's no-show, another mystery about yesterday's NPD numbers was the absence of two of the biggest games of the season. Nowhere to be found were Guitar Hero World Tour, the newest entry in Activision's billion-dollar rhythm series, and Rock Band 2, the latest installment in MTV Games' own seven-million-unit franchise. How could these two headline-grabbing, money-minting franchises be missing in action?

The answer is simple. The NPD Group, the US' game-industry research firm of record, issues its best-seller lists based on SKU (Stock Keeping Unit), retail shorthand for a single product. Each iteration of a game on a different platform is its own SKU, and every subconfiguration--bundles, special editions, etc.--is also a different SKU. With no less than 11 Guitar Hero World Tour and four Rock Band 2 configurations, the two games simply spread themselves too thin, SKU-wise, to make the cut.

Now, the release of the raw October NPD data allows for the tabulation of the two games' total sales. Unsurprisingly, Guitar Hero World Tour, available on four consoles, was the winner with just over 534,000 units sold for the month. The most popular platform was the Xbox 360 (190,000 units), followed by the Wii (182,845), PlayStation 3 (96,657), and PlayStation 2 (63,462).

Rock Band 2's second-place finish wasn't too shabby either, with sales split almost evenly amongst its two platforms. NPD reports US retailers sold 238,128 units of the game during October, 119,569 being of the 360 variety, and 118,559 bearing the PlayStation 3 mark. The PS3 version of the game went on sale October 17, nearly a month after the 360 Rock Band 2. Wii and PlayStation 2 editions are expected next month.

Unfortunately, October was not nearly as kind to the third instrument-based rhythm game released during the month, Rock Revolution. According to NPD figures, Konami's critically savaged title sold under 3,000 units across the entirety of the country during the month. According to the data, the game sold 1,442 for the 360, 816 for the PS3, 666 for the DS, and only two copies for the Wii.

Requests for verification of that suspect Wii figure had not been answered by NPD nor Konami as of press time. However, it must be noted that NPD data is from a survey of retailers, so it's likely a number that low is some sort of statistical mistake. Adding to the mystery is the fact the Wii edition of Rock Revolution is currently out of stock on Amazon.com, and rumors of shipping problems from the manufacturer in Asia.+

I don't know what to say...it's some kind of funny