So which era was best?
1,2 - Brooks, Groening, Simon
3,4 - Jean, Reiss
5,6 - Mirkin
7,8 - Oakely, Weinstein
9+ - Scully and then I have no idea (can't imagine anyone will pick this anyway)
I prefer Mirkin's years by far, but the Jean/Reiss years were classics in their own way. Wasn't crazy about the Oakely/Weinstein years, which is funny because I loved the episodes they wrote before they became showrunners. But they still produced several great episodes, and those are clearly also 'classic' Simpsons years unlike the garbage that followed.
Edit: Forgot to rate 1 and 2. Find season 1 pretty unwatchable unless you're looking for how it all got started. Season 2 feels a lot like slightly conservative and raw Jean/Reiss to me, and I'd actually always assumed that they were showrunners for this year too. The second half of that season is where I think The Simpsons really took off.
For me it has to be season 3 through to 9 with my personal favourites being 4, 5 and 8.
I definitely agree that half way through season 2 is where they really hit form.