To me the following have been exceptional
-Before Watchmen Minutemen
-Before Watchmen Nite-Owl
-Before Watchmen Silk Spectre
Before Watchmen Comedian started off with a bang, but I thought suffered a drop off in issue two and I'm borderline debating about dropping the thing. The art is fantastic.
Before Watchmen Ozymandias was exceptionally good, something that surprised me since I'm not really a fan of the character or Len Wein, but he did such a great job.