Glee is popular because it deals with complex issues like, gay issues and teen pregnancy in a sensitive and progressive way. It is also popular because the characters and all the dynamics are complex and most of them are very likable. The show is also funny and has a nice balance of original songs and traditional music songs.
Glee has everybody. Gay couples (girls and boys) different ethnicities (Santana Tina Mercedes) different religions (aethism Kurt Judiasm Rachel and puck) eating disorders (Mercedes season one) teen pregnancies (Quinn and puck) divorce (terry Nd will) domestic violence (coach beaste and Cooter) transgender (unique) umm...bullying (everybody) suicide (David) discovering sexuality (Blaine, blame it on the achohol) disabilities (becky Jackson) stereotypes (the mean cheerleaders) people who think they're the best (sugar) Nd they're singing is amazing. I am a gleek to the end <3