If I were pressed to give a definitive answer, my favorite era would have to be the original, dork age gag era. Bad puns and all. Gallagher is so much cheesy fun, with wild swerves in pitch black horror comedy, but Penders kind of wrecks everything he touches, and then DeCesare is in there quietly getting the assignment better than anybody else up until Flynn. It's a real shame DeCesare wasn't put on more stories.
Flynn is also great, and I almost prefer his post-reboot work to the gag era. IDW is kind of hit or miss for me though. The characters are great, but the pacing and world building leave something to be desired.
But the less I say about ASO, the better. The art's often great, and that's the only praise I can give it.
I'd be happy to give you a look at the sourcebook once it's a little more cooked! I've got all the setting info written up. Just need the NPCs and character generation hacks. Then I can get to work on the art.