True, but it depends on what the player gets out of it. Take my favorite 3DS game, Zero Escape: Virtue's Last Reward. It easily has the greatest storyline I've ever seen in a game, and I absolutely loved the story because of how long it lasted. Now, they did add a few things for replay value, but if they hadn't added them, I'd still be satisfied because the game was that good. It was pretty long, too. The Ace Attorney games are the same way (though I've replayed all of those).
I think the important thing is the amount of time you spend and the satisfaction you get out of it compared to the price you're paying, because many game developers feel that the immersion would be ruined if they added something else. There are some games that want you to finish the game and leave you with the feelings that you were left with at the end. A good example of this is Bioshock Infinite, and a much more general example is most Adventure and Visual Novel games. After all, sometimes developers do try to add extra content to their great experiences and they end up feeling tacked on, which can sometimes be the case with multiplayer in various games (and the vice versa is true for various multiplayer-oriented games like Call of Duty and Battlefield 3).
I'll agree, though, Brawl's story mode was just okay. Other than the cutscenes, the gameplay was just okay, but it mostly just felt like a segue to the next part of the story. Cut out the gameplay, and you'd practically have a movie. A short one, though. But it did have a great presentation.