I would say the 60s and 70s. Best time for rock music. I like 80s music the second most. I don't listen to that much 90s music but there's some bands I like from that era. I don't even bother listening to the music today.
1980's and 1990's for me, with a bit of 70's thrown in as most bands started around 1975-1977ish....
In the late 70's and early 80's, there were all the great new wave bands. The Cars kicked off about 4-5 really killer New Wave albums, Loverboy put up their best stuff, Journey Had Perry singing and did not become totally ballad-ized, Night Ranger were sort of a pre-Hair Metal/New Wave hybrid, STYX from the early 70's before they went Music Time on us. ZZ Top and Heart with Blues and Folk roots that sounded cool respectively.
In the 80's, all the great diverse metal came from there - Metallica, Dokken, Iron Maiden, RATT, Van-Halen, Whitesnake, Megadeth, Slayer, Def Leppard, Motorhead (well, 70's too for them), Lee Aaron, Girlschool, Lita Ford, Ozzy Osbourne, Dio, Black Sabbath, Deep Purple, Rainbow, The Scorpions, Skid Row, Bon Jovi, Pantera in their glam phase, and the list goes on and on and on, it's Heaven and Heck....
THen the 90's came, there was all this great indie and underground stuff coming to the top like - My Bloody Valentine, Nirvana, Stone Temple Pilots, The Gin Blossoms, Bush before they went Techno, Soundgarden, No Doubt, The Red Hot Chili-Peppers, R.E.M. (who were also around and kicking pretty hard in the late 80's).
If you're referring to trance, I'd say the 2000s have been the best so far. There was some good stuff in the 1990s, but some of the stuff I've heard lately, especially from Germany's ATB, has been so insightful and thought-provoking (especially his 2003 album "Addicted to Music")
American, I like the 30s and early 40s the best. There is some good stuff from America from 1946-2001, but almost nothing worth even mentioning after 2001.
Of the four most recent completed decades, I will probably have to choose the 1960s for consistency in good music.
If I had to pick just one decade of music I suppose it would be the 70's. I could easily go with the 60's but if I'm going just by my personal favorite stuff then it's the 70's for sure. Overall I'd say my favorite 20 year span in music would be 1965 through 1985.
I can't narrow it down to just one. Every decade has contributed something to my pop-cultural being. To say that one decade is the best just can't be done. You're only setting yourself up for a heated argument.
I will say, though, that I don't think that 80s music is cheesy. Of course, that's just my opinion. I enjoy all 80s music with all sincerity, and you can quote me on that.