Actually, I don't think I misunderstood you. I may have expressed a bit of hyperbole. I do that a bit too much (some would say doing it at all is a bit too much).
When I was six, I may have won a fight with a dragon or a horde of orcs... but I never "won" pretend. I moved on to rescue the princess or retake the fort or whatever the end of the story was. Killing the baddies was a step in that process.
It was an important step. It was certainly an energetic step. But it was not what won the day.
Tell that to the player of the Cleric that was going to die from multiple swarms until the Wizard Thunderwaved the swarms into a deep pit.
In this case, the Wizard won the day and it wasn't by rescuing the Princess. It was by winning the encounter and saving the Cleric so that the PCs could go rescue the Princess. It's part of the journey. Rescuing the Princess is the goal, but the challenges to getting to that goal are the journey and every single step along the way should be as much fun as achieving the final goal. Otherwise, why play the game if each step isn't fun?
I'm still inclined to disagree. Some of the most interesting and enjoyable encounters of my RP career have been TPKs or near TPKs. Two of the more recent ones (the ones since we started playing 4e) still get joked about and revisited in other sessions and beer nights.
You and I enjoy different aspects of the game. That's cool. The most important part is to have fun.
Hard challenges? Fine. Near TPKs, ok. Not everyone is always going to survive. The game is not fun without risk.
But, TPKs are a game balance issue since intelligent PCs should run away when things get too tough. Dying and not achieving the overall goal is not heroic, it's just a waste. If the PCs are prevented from running away (i.e. the DM traps them or has the bad guys hunt them down), then what's the point of playing? To start up again and be defeated and humiliated a second time?
I love a good challenge. I enjoy the bad guys overwhelming the PCs and the players have to come up with interesting and clever solutions in order to win.
But most TPKs, at least in the "hard to kill PCs" 4th edition, are the result of a DM not understanding the synergy of his monsters and creating too tough of a challenge (sometimes by overestimating his players, sometimes by underestimating the synergy of the monsters), or extremely bad dice rolls (sometimes, a combination of the two). In the former case, the DM should be smarter than that. It should be his job to go over his monsters and make sure that they don't have a TPK combo (like multi-PC Stunned and Autodamage, or whatever) In the latter case of bad dice rolls, the PCs should run away and some of them should survive. If the DM hunts them down and kills them, then that's not fun either.
Sorry, but TPKs are typically not as fun as you claim, especially if the players are really into the adventure/campaign. It's like watching half of a movie and then the good guy gets killed and the movie is over. We don't find out if the hostage was ever rescued or if the nuke goes off. Sure, you can start over with new PCs in the same adventure, but that's kind of lame too.
I can see that if an adventure arc was boring, then a TPK would be no big deal.
But, your "TPKs are interesting and enjoyable" idea sounds overrated. TPKs are very memorable. Everyone remembers when the entire party got smoked. But, they're not especially enjoyable. Talking about them over beers later on is talking about something that is memorable. Memorable is not neccesarily the same as enjoyable. I suspect that most players don't really enjoy TPKs, especially here on PBP where it takes an entire afternoon to get a new PC up on to the web site. Dying here is a pain in the butt.