The first part of that title is purely subjective, but according to the article in the upcoming issue of GamePro that reader Mobius0077 posted in TVGB's Community Discussions area it is entirely true. That's right, the subheader of the article claims that from the time they spent with Call of Duty: World at War it is actually better than Call of Duty: Modern Warfare. After reading the article and pretending it wasn't a total fluff piece TVGB can see where they're coming from.
Updates:
The article also says that GamePro will be running a contest to get players into the open Beta at win.gamepro.com/callofduty.