The 2000's were like the 1970's, in which simple songs with dance beats were the norm. Much like people couldn't differentiate between different disco groups of the 70's, pretty much every female pop star of the 2000's sound the same.
I think the best eras of music were the late-1960's and the early-1980's. Those time periods were like vaccuums for music, with a lot of experimentation with new instruments and new styles, but nothing so dominant that everyone merely copied the "in" sound.
My $0.02.