Hmmm, can't say that I agree with Jim here.
I think the issue is that in previous generations of games, a gamer who didn't have a certain degree of skill (which might go beyond practice) simply could not finish the game. If you couldn't beat a level, then you weren't going to be able to see the next level. People bought and played games for dozens of hours without ever seeing all of the major content, and part of what made a lot of gamers good was being able to see all of the major content in their game.
Things like "Kirby" show a modern game developer mentality, of wanting to make games easy enough so that anyone who plays it can feel like they are good at it, and are a winner. Basically, if you buy the game, your thus entitled to playing all the levels/through the whole story, and getting the "you win" at the end. It's sort of like schools catering towards the "self validation" of students, rather than education.
Saying that pursueing things like gold medals, gems, or whatever else makes games "challenging" is kind of silly to be honest, unless reaching those plateaus is required to actually advance. Say needing a gold medal on a level of "Kirby" before being allowed to advance to the next level.
In the end such systems are not really all that differant from one of the oldest video game conventions of all the "Score" which is registered as you play. Argueing that the challenge should be viewed entirely as aiming for high numbers of points, is actually a sort of de-evolution of gaming. In general, rewarding people with progression and making getting to the end of the game the major point (with the score being used to fine tune performance and compete with other experts) was part of the evolution of video gaming away from the simplest games like "Space Invaders".
Ultimatly this kind of conflict is largely between the serious gamers, and the desires of the industry. The serious gamer wants games that they can beat that not everyone out there can (that aren't parodies of the idea like "I want to be the guy"), it to have some meaning to say they actually finished the storyline/levels in a game, as opposed to it being something where pretty much everyone who plugged in the game and was persistant enough could have done so, leading to a discussion involving everything from serious gamers, to little kids, to the elderly about potential plot points or whatever. Your serious gamer wants there to be games that other people want to play and beat, but can't, yet they can. The gaming industry however wants to produce games that are as approachable as possible, to reach as many people as possible, and sell the most potential units, and they won't acehive that goal with games that are too hard for the casuals. Casuals will still play hard games, but there will be less of an audience for a product your typical player can't finish.
It's a big issue, and in the end it's one that won't end well for serious gamers, because there is just too much money for the game industry to make out of holding the hands of causual players, and making games that anyone can beat without a huge amouint of skill or hundreds of hours of time investment. Not to mention that as much as we gamers want long games, the industry seems to realize now that a game that is hundreds of hours long shoots themselves in the foot, after all if people can play the same game for a year or more and be content, they won't be buying more games during that time period usually.
I don't think gamers adjusting their attitude back to the level of "astoids" and playing entirel for score/gems/performance points is really a viable solution, or that the idea adds anything to the overall debate. In the end I think it's just a situation where there is no answer, and the serious games lose because the casual market is too big, and the game companies too greedy.