I'm only 31, but that's in hexadecimal.

(To those of you who can't translate hex to decimal I'll make it easier: Today I am 18,047 days old (I make it a habit to always know how many days old I am).)
As someone who has walked that walk, I can honestly say that my 40's (in decimal) have been my favorite decade of my life.
Now, what you have to realize is that I'm taking things as a whole. There were spikes of fantastical, amazing things that happened in my teenage years that I can't match in this decade. But they were surrounded by the typical teenage issues of stuff like having little freedom. Being stuck at home wishing I could go do... stuff. Anything. Not be bored just watching TV or doing homework. Being a teenager sucks compared to adulthood. But I did enjoy the hell out of those years since at the time it was the best decade of my life. And some of those memories are AWESOME. But they were surrounded by loads of stuff that was far less than awesome.
My 20's were WAY better. Much more freedom. College was crazy compared to high school (I managed to get a 4 year degree in only 7 years). Road trips. A month bumming around Europe with my best friend. Marriage. Yep, way better than those teen years.
But not better than my 30's. First career-oriented job (I was slow to actually get a "real job"). First house. First big-screen TV. The amount of expendable income, and quality leisure time available in my 30's was higher than in my 20's. In my 20's the actual amount of leisure time was greater, but it was mostly dead time since I didn't have much income to throw into it. The leisure time of my 30's was QUALITY time compared to my 20's. We'd take fantasy weekend trips to Vegas or Phoenix (we did a quick trip there to see the Cowboys play out-of-town once) for the fun of it. My wife and I would experiment with what we'd do in our non-working hours to see what we liked and didn't like doing. It was GREAT!
By the time of our 40's we began to expand on our fun time, not wasting much time experimenting, but concentrating on the things we like best. Hosting more, and bigger, parties. Taking trips that we KNOW we love (cruises, the beaches of Mexico, etc.). The main experimenting I do nowadays is in trying to figure how my favorite recipe for my Margarita machine. I was out of work for over 6 months last year, and I ended up having the greatest Summer of my life!
Yep, if I had to relive a decade it would be this one. And my preference goes down as the age goes down. And I'm looking forward to my 50's in a few months. As I have gotten older my expendable income has gone up (though I took quite a bump being out of work), the control over what I can do has gone up, and my leisure time went up (well.. until we adopted those kids of ours a couple years ago). As a whole, the quality of my life (and of my toys) per decade has gone up. Some individual years sucked, but hey, that's how it goes, and that's true in every decade.
On the whole, getting older has rocked for me.
Your mileage may vary.
Live long and prosper.
Bunsen