First off the Wii Mote was released in 2006 the same year the Wii launched. So I assume you must be talking about the Wii Mote being sold with a lesser game Wii Play in 2007. The Wii Zapper I was also sold with what was essentially a "demo game" in the same fashion with the Link Crossbow game. I think Nintendo threw them in to add value to games that really wouldn't have been worth the cost if sold on their own. As far as the Wii Wheel it was also originally also packed in with Mario Kart, but I am sure that was more a way to spur additional wii wheel purchases because I know it worked with me buying a second wheel the day it came out. I don't think the Motion Plus was able to pull off additional purchases the same way despite being included with a few games. I've never seen official sales figures on the Wii Speak but I don't know of anyone that actually bought it and that would explain its quick disappearance.
The "most successful" years of the Wii that you mention is more of Nintendo was able to catch lightning in a bottle twice. First with Motion Play and Wii Sports and a steady release schedule of AAA games in the beginning and then just when there was a hint of Wii supply catching up with demand Wii Fit was released and brought along a lot of casuals who were originally on the fence and every soccer mom that was duped into thinking it was real fitness product.
