It seems a little naive me saying that my favourite decade of music is the noughties (00's), but it would have to be true. I definitely appreciate old music and don't discriminate against music based on the year it was made, but just the sheer number of different styles that have come out of this decade and the quality of the music being made if you look past what's on the radio - it's just amazing.
Think about it, the decade starts with some great 90s bands like At The Drive-in and Rage Against the Machine still going, the beginning of the White Stripes (well, really 1999 but you get the idea, 2000 is a close enough estimate as they were around then), Explosions In The Sky (playing a whole new style of music). Then you have the beginning of Broken Social Scene and the Canadian indie scene starting up, Metric's earlier stuff, The Strokes - which brought back garage rock in a new style and made lo-fi popular (and in the opinion of some people saved rock and roll). The Black Keys come in soon with their ground-breaking two piece blues/rock combination (admittedly influenced by Junior Kimsbrough and R.L. Burnside but still a very distinct new sound), The Libertines came out. More acoustic music like Kaki King and Jack Johnson emerged, hardcore music developed with bands like I Killed the Prom Queen, The Kills came out (drum machine songs made a comeback around this time), Love of Diagrams began in Melbourne and the Yeah Yeah Yeahs began. Bass guitar and drum two-piece bands started cropping up (Death From Above 1979 for instance), and of course The Edmund Fitzgerald, which completely defined a whole genre of music for me and a bunch of other people using disjointed rhythms to make math rock. New wave sounds and synth pop made a comeback, bands like Foals and Wolf Parade came out. A new type of folk music was coming out (ie. not Bob Dylan Folk), as well as bands like Beach House who blended electronic sounds with folk music. Bands like Sonic Youth and Blonde Redhead are still pumping out music. A whole branch of different sounds unique to individual bands were coming out, such as My Disco's minimalist tunes, I Heart Hiroshima's bass-less line up (two guitars and drums) and even mixes of jazz and classical sounding piano with elements of math-rock and fusion (Mouse On The Keys). Some cool pop music came out like Phoenix, some awesome math-rock from Japan (see Lite or Toe). Experimental electro like Crystal Castles comes from the 00's, as does the post-hardcore sound from bands like Die! Die! Die!, La Dispute and previously mentioned Love of Diagrams. And of course, the beach/surf sounding lo-fi indie currently coming from New York, with amazing bands like Beach Fossils, Vivian Girls, The Babies and Real Estate. There's just so many amazing bands and new genres that came from that era (and continued through that era) that you just can't say no to.
tl;dr: The 2000s had an explosion of new and unique sounds and a load of great new bands providing you listened past what's on the radio.
If I was going to put the decades in order, it would go like this:
00s > 80s (no wave, grunge, new wave) > 60s (The Kinks, Hendrix, enough said) > 90s (some awesome music from the 90s but not enough to rank it highly) > 70s (like the 90s, great music but I don't listen to enough of it to rank it highly)
Also, I'd like to mention the 30s, 40s and 50s, which had some really great blues music from the likes of Son House, Robert Johnson and Muddy Waters just as examples.