The problem with that argument is that dealing with the exact same thing constantly quickly grows boring. I used to have fun with 2D Mario platformers, yeah - most people do - but if they're just going to keep doing the same thing with the same exact formula over and over again, I'm going to get bored quickly and move on to something with a little more originality and intrigue. There's really only so much you can do with a license before everything about it just starts to seem redundant and tedious, at least to me.
And as a "games are art" hippie, I believe games have immense potential to be innovative and deep without sacrificing fun. Even ignoring my incredibly pretentious "oh I'm so smart, I can play a game about how full of shit Ayn Rand is and appreciate it, nweeeeeeeeh" attitude, I just want to see more games with more unique thematic design and gameplay that tries to push the envelope. The chubby plumber is not either of those to me.