1. Demographics - It's definitely fair to say that the HD crowd are a little more enthusiastic about getting their products day 1. They pre-order, line-up, and watch release dates. Wii owners are more likely to go down to the game store once a month and look for something which they played at a friend's house or saw in an ad.
2. Retail Support - This plays into point 1, but gets into a bit of a chicken-and-egg dilemma. A lot of Wii games are hard to find first day. Either they don't make it onto shelves, or too few make it onto shelves. Buying a Wii game on day 1 can be really hard to do sometimes, and personally, I've given up trying. Zack & Wiki, No More Heroes, CoD:WaW are all titles which have been known to be hard to find for the first week after release, and I know there are more. So do retailers not bother because the 1st day crowd isn't there for these games, or is the 1st day crowd not there because the retailers don't bother?
3. Install base growth - This doesn't explain small launches, but it does explain long legs. The Wii userbase is growing at a breakneck pace, and all those new users have to catch up on the game library. So they check out what got good reviews or what people tell them is good and start buying games. The HD consoles aren't growing as fast, so they don't have such a long tail.
"The worst part about these reviews is they are [subjective]--and their scores often depend on how drunk you got the media at a Street Fighter event." — Mona Hamilton, Capcom Senior VP of Marketing
*Image indefinitely borrowed from BrainBoxLtd without his consent.
