It is feasible to compete at many things which are not interesting competitively.
Just because something is competitive doesn't mean it should be, or that the competitive experience is satisfying or fun.
Poor competition in sequels is, at least from my experience, a primary reason why many die such quick deaths. Competition fuels longevity. Casual players can look up to the best players and say "Wow... I don't have any interest in that, but ****, this game is pretty awesome. Those players are awesome. That's amazing." Alternately, they can say "****... I am going to be able to do that one day," and another competitive player is born. This fuels interest in the game, even amongst casual players. Spectating is fun; surely all of you have watched the Olympics, watching games you've never even played before, and been **** impressed.
As a mental exercise think back a few years to when Shined Blind originally came out and/or you first saw it. What did you think about it? For those without lots of competitive experience it was a real eye-opener. I know relatively casual players who saw that video and their opinion of smash shot way up, as well as their interest in playing the game, even if they didn't really ever intend to improve. Just knowing that the game was so much more involved than they thought possible excited them.
A game which doesn't support high-end gameplay tends to die quite quickly. Don't take this to mean it wouldn't sell well. After all, we have Brawl, countless Mario Parties, and whatever. But how many of those players will actually keep playing the game for any consistent amount of time? They won't, after the initial fun wears off it'll be pulled out occasionally at best. The longevity is not the same, the excitement is not the same. The game dies, people stop caring about it.
A game with no high-end gameplay is almost always flawed at the middle-end, too. That is, as a player attempts to get better he'll start to notice all the types of things that make it no fun for good players, and start to realize that he may as well not bother; if he keeps improving then the game will die for him. Such a game is only satisfying for any stretch of time to the most casual of gamers who are just button mashing.
There is a vast difference between playing a game competitively, and playing a good competitive game.