Before Must Love Dogs, before Serendipity, and well before America's Sweethearts, John Cusack was a man who stood for something: A world where it was okay to daydream about burgers coming alive and drawings jumping off of their multi-colored pages. The more blatant fantasy movies of Better Off Dead and One Crazy Summer (referenced above) became something of a signature of the John Cusack film in the eighties, but something happened to Mr. C in the wake of his post-eighties success. He started picking roles steeped in reality.
This is not to say that Cusack does not still appear in many a cherry of a film; there are even years when he returns to his phantasmagoric roots as with Charlie Kaufman's Being John Malkovich. It's just that he's become one of those prototypical awkward leading men, a concoction helmed by Woody Allen, but never to be replicated quite as well. In his quest to be the go-to man for the offbeat lead in comedies like Grosse Pointe Blank and High Fidelity, both of which are some of the better movies in his repertoire, Cusack has lost that certain magicality possessed by Gib in The Sure Thing, Lane in Better Off Dead, Hoops in One Crazy Summer, and even Lloyd in Say Anything, the film that arguably solidified Cusack's transformation into the peculiar, but endearing counterpart to the normal, out of his league girl that appeared in all of the aforementioned titles.
This metamorphosis is, yes, in part due to his actual aging process and the quirkiness being mistaken for creepiness at an advanced stage in life, but also in part due to the inevitable selling out process of being an actor. Let me emphasize, however, that the case against John Cusack is not a malignment of the actor himself, so much as the profession. There is typically a point in every actor's career when he or she caves to the pressures of turning his or her niche into something commercial (i.e. Michael Cera, Johnny Depp, Zooey Deschanel).
The reliance on typecasting of sorts is the mutual fault of actors who can't say no to that sweet, sweet check and the men with the money who can only see them a certain way. Only a very rare few can be credited as multi-faceted. Sean Penn comes to mind. This was a man who played constantly stoned surfer Jeff Spicoli in Fast Times at Ridgemont High, eventually to trade in that surfboard for an old professor comb-over in his role as San Francisco's first openly gay politician Harvey Milk in, you guessed it, Milk. John Cusack is not, unfortunately, in this multi-faceted category. He is brilliant at what he does, but it no longer looks quite as appealing as it did about twenty years ago.