I know I really felt the loss of Dr Mark Greene from ER in 2002. I sat and cried along with thousands of others around the world when the character slipped quietly into death. I cried with the same people when he was diagnosed with terminal cancer and cried again watching Elizabeth (Alex Kingston) try and go on without him. Dr Greene was, to me, a hugely integral character in teh success of ER in the early seasons. He was mentor, best friend, lover, father, doctor extraordinaire. From looking after his ailing father to marrying Elizabeth, Dr Greene did it all on the show and the show was and is better for having had the character there at all.
Keep the good ones coming!