this is a very good discussion. and one I have heard again and again. On the subject on death...
we die so others may live. simple. like you said overpopulation would be a huge issue and thus the planet earth would become inhabitable.
on the subject of immortality...
immortality cannot be achieved in the real world. vampires, werewolves, witches, and other mystical creatures that breathe immortality don't not exist (and if they do, for all the sci-fi/ fan-fic lovers, then they know better than to reveal themselves). immortality is actually something I would like to have....and for very self-fish reasons I might add...I'm only self-fish in two aspects and thats my birthday and the subject of ever-lasting life.
yes, watching my loved ones die would b tragic, but let's face it....they're going to die anyway. my parents, i love them, but they will die. my friends, i love them, but they also will die. before or after me no one knows. if i were to become immortal i will get to see everything. my life will evolve with the earth. i want to know what happens in 200 years from now. how far humans have gone...or how far we have fallen. sure my reasons are self-fish and unpredictable, but they are my reasons....and at the end of the day it's all about #1...because all you have it yourself.