We had a lot of old timers at our shop so I got a taste of what the old Magic was like. We also had plenty of Onslaught/Invasion/Odyssey packs (and the smaller sets that goes with them) to do drafts of those.
Somehow I found the game getting overly complex after Mirrodin.
Complex
after Mirrodin? Did you play Odyssey?! Now
that was complex!
Those two sets are, personally, my two favorite sets/metagames of all times though I do have a thing for Ravnica. Funnily enough, one is the most sold of all times (Mirrodin) and the other one the worse sellers of all times (Odyssey).
As for the flavor, you should check Magic 2010.
They realized that they have been sacrificing the flavor too much and have tried to put more flavor in that set.