Ghost-type Pokemon, however, do not die. Also, I'm pretty sure that Legendary Pokemon are supposed to be immortal. --- http://i458.photobucket.com/albums/qq303/ CharizardFire6/Char-Brawl.gif?t=1223088742
When Pokemon die they turn into wild Ghastly and Misdreavus. And even Ghost Pokemon eventually vanish into thin air one day..
Also, some say that Wild Pokemon die, not faint. Even though its impossible to prove it kind of make sense and explains why trainers can't capture fainted wild Pokemon, because they're useless when dead. And assuming they faint, they have no trainers to heal them so they will most likely die anyway if the wounds are serious.
"Should the opponent's pokemon die, what should have been done about that? What if the opposing trainer feels sad/horrified at his precious pokemon dead? Unless there's a way the pokemon center could somehow magically resurrect them, then the whole pokemon population will eventually be extinct at this rate. What's the trainer going to do about the dead pokemon?"
Team Rocket was the only team who actually killed Pokemon. Remember Cubone's mother..
Who can forget the only uncatchable boss Wild Pokemon? They need more of those, by the way; to make it more challenging, they can screw with the beastie's stats, since the thing can't be caught anyways. --- Only losers sig their own quotes! - Me ...you copy vacuum cleaners. [...]Because you both suck. - NGW
Gameplay-wise, dying Pokemon would be stupid (my level 100 Pikachu perma-died to an a**hole trainer who just threw 6 untrained freshly caught level 50 Rattatas at me! WTF?!).
Movie/anime-wise, Pokemon die its just not blatantly stated outright in order to keep its G-rating. (I think theres like a whopping total of 4 Pokemon that has been stated/implied to have died in the entire 1000+ anime episodes)
Manga(comic)-wise, LOTS of Pokemon die but the mangas aren't published in the U.S. anymore so not many people know about this.