1) More episodes to develop the characters and their relationships.

2) It's an ensemble where every actor gets their time to shine.  It could have just been the Michael Scott show or even focused on the four leads like the UK version, but everyone is a distinct and hilarious character.  I can't think of many other shows where a background character like Creed could steal entire episodes ("I like to steal things.  It's what I do.  I stopped caring a long time ago,").