I definitely listen to the 1970s music the most, as that's when most of my favourite bands released their best material (or, in the case of bands like Lynyrd Skynyrd, their only definitive albums) - a big chunk of the albums I own came out from 1970 through to 1977. I also have a few albums from 1979, although 1978 is not as well represented.
I do listen to a fair bit of music from the 1980s, although a lot of music most strongly associated with that decade isn't to my taste I think this is compensated for by quality bands like Dire Straits or U2. I don't listen to '60s music as much, but I think this is more due to relative lack of exposure on my part - I'd probably enjoy the latter part of this decade in particular quite a bit if I got into it. I know very little about 1950s music, as this is before my parents' time, let alone mine, and beyond the obvious artists (e.g. Chuck Berry) I've never heard any of it.
I have to say I do listen to post-2000 music a fair bit, although with a couple of exceptions this is largely not through my own choosing as the rest of my family listens to more contemporary music than I do and often the music of choice on car journeys is from this era (either CDs or my sister's iPod
playlist). I haven't found much I like from the 1990s, most of what I've heard just doesn't appeal to me.
If asked to define my favourite era of music, I would say it ends around the rise of punk and disco in the late 1970s, although I can't quite put a date to when it begins - I'd guess it would be some time between 1966 and 1969 but I'm not familiar enough with the late 1960s to date this accurately.