I think this years game of The Beatles: Rock Band is going to be better for Harmonix and will (hopefully) sell more than Guitar Hero 5. My opinion is that the Guitar Hero brand has been over used this entire year and has loss its former glory since GH3. It only sold the same amount as The Beatles in its opening week due to it selling to their hardcore fan base and with the extra copy of Van Halen but The Beatles: Rock Band is different. The Beatles: Rock Band will continue to sell year round just because of the band its associated with and is a full Rock Band experiance built from the ground up unlike other band games like GH Aerosmith or Metallica. It is also friendly enough to be selling well to casual players for the Wii just because of its colorful, trippy graphics. It's outselling GH5 for the Wii 2-1 and even though you said that Rock Band is a weaker brand in Europe, it will eventually catch up with many older, Europeans who are in their late 40's/ early 50's, when the marketing catches up, will just give them a taste of playing and listening to their favorite, most popular music band back in the 1960's(and all time) and relieving their experiance of the band.
The Beatles will keep selling year round to younger, family Wii players and to older, Europeans which gives the game a broader user base. And with a collectors CD coming out with the best music from The Beatles that came out as the same day the game came it, it will also appeal to a new generation of listeners and give this game a try with it also selling to the usual hardcore Rock Band players. Hopefully, all of this can start The Beatles revolution again 
