Let's cut to the chase: 4/5 stars. Most of the credit goes to Joseph Gordon-Levitt for a stellar portrayal of 27 year old man hit smack-in-the face with a cancer diagnosis.
Joseph Gordon-Levitt is an excellent actor. He's been at it for a long time. Let's not forget, he spent several of his formative years playing an elder alien man living life on earth in the body of a teenage boy ( 3rd Rock from the Sun). That can't have been easy.
In 2007, he portrayed Chris Pratt (The Lookout), a young man who was once the king of his high school, but after a tragic and foolish mistake, lives the difficult life of someone with permanent cognitive impairment due to traumatic brain injury. Although he'd had a steady career all along, this seemed to be the point when people really took notice of JGL as an adult actor.
In 50/50, he manages to play the role of "normal, nice guy", so incredibly well, you feel certain that he is, in fact, that guy. Interestingly, he was not originally cast in the role, but rather, filled-in after James McAvoy had to drop out. It's hard to imagine anyone capturing 'genuine' quite as well as Joseph Gordon-Levitt. In both the 'regular guy' moments, as well as the 'devastation of cancer' moments, his expressions ring fully true.
As you've heard, this is a funny cancer-movie. Seth Rogan is funny. Still, you wonder, at some point, why this "nice" guy is hanging around with a guy whose maturation is about a decade delayed. But the movie is able to make it work. You don't doubt for a minute that Seth's character loves his friend, Adam, and will stick it out with him for better or worse---unlike Adam's girlfriend, Rachel.
There were a couple of things that I think would have improved the film:
I would have liked to have seen a few lines, early in the film, showing that Adam has concern for the terrible disease from which his father is suffering, and is aware of the toll this has to be taking on his mother. "Hey, Mom, let me hang out with Dad this weekend. You need to take a break---go have lunch with your friends or something." I would expect that from the conscientious Adam.
I also think the film would have benefited from a more sympathetic portrayal of 'the girlfriend', Rachel. Maybe there really are people who are that unlikable, but I doubt that Adam would be spending every night with one of them. It would be more realistic to focus on the fact that they were mismatched to begin with, she was not well-liked by his parents or his friends, and, sadly, both she and Adam felt stuck because it seemed like a bad time to pursue a break-up. Instead, she just comes across as a weak, shallow bitch ( i.e. not the type of person someone like Adam is likely to be involved with in the first place).
On the whole, though, it's a very simple, straightforward film, and in this case, that's a real compliment.
I'll be seeing a couple more movies this weekend...so stay tuned.