I wasn't here for about three quarters of the game, and most of the current users joined even later.
In all of my years there's been a fatal pessimism due to "inactivity," and generally one party has had a significant advantage over the other.
I'd like to see someone like Yankee/PiT/Lumine/Windjammer/Adam take a shot at this, in detail. Although they might just say the years right after they joined like tmth did
(That being said I'm sure most people had the most fun when they were still fairly new. Kinda like how people generally listen to the music they heard as a teenager. It's a subjective question.)
I guess one way to look at it objectively would be to look at frequency of posts/bills/voter turnout in different eras. (Not the easiest job, though.)