You're comparing launches but the real concern is what the Wii U has to face NOW. Games plus new system announcements. This is the competition for the next few months.
The fact is that new consoles always have to compete with new releases on older consoles. Yes, it's something that gamers have to consider, but it's no more "real" than comparing launch-to-launch.
The launch-to-launch comparison is valid because it puts the Wii U launch in a historical context. Some are trying to make the Wii U to be in a bad position, but it's really no different than what's happened before, unless you want to deny the fact that the 360 didn't outsell the PS2 for several months.
So, don't discount the historical just because it doesn't fit what you want to want argue. It's a valid and true comparison.