When I re-watched The Wire the season 2 plot was my favorite with Ziggy, The Greek, Sobotka, Nick, Sergie the russian and the connection with Prop Joe. Then you had all the separate stuff with Barksdale, Stringer, Omar etc. still going on. Season 2 had the most complex plot and interesting characters. The season 4 and 5 plots (school and fake serial killer) were really bad seasons, especially 5.