Having lived in NYC and LA... I have gotten to experience the best that fast food burgers has to offer aka Shake Shack, Five Guys, and In n Out. There has been plenty of debate on which of these three is the king of the fast food burger (yes any of these are way better than McDs, Burger King, and etc...). I will outline my take here.
For the best value for your buck... it is In n Out. You can get away with a fry, burger and a drink for five dollars... which I think is ridiculous given how great tasting the burger is. There is a caveat for me though. I feel like the burger doesn't really taste good unless you get it "animal style" which is basically substituting the onion for grilled onions. The ingredients are fresh and they blow away other fast food chains. For five guys you are looking at five dollars for the burger alone and for shake shack unless you get the crappy plain burger your look at close to 10 buckaroos (the shake stack... i.e. the only burger you should eat from there) for the burger alone.
Five Guys has the best fries hands downs... assuming you like cajun fries. They are steak cut fries that they make from freshly cut potatoes (cut in the restaurant) seasoned heavily with cajun spices. The size of the fries can be deceiving in a good way; they always poor an extra handful of fries in your bag on top of the cup of fries they give you, which basically doubles the quantity of fries you get. I wouldn't really bother with the fries from In n Out or Shake Shack unless you really want them. In n Out fries are made from freshly cut potatoes, but are usually soft and limp and Shake Shack fries look and taste like the ones you get the cafeteria in school... I mean they aren't horrible, but I just end up drowning them in ketchup while with Five Guy's fries I do not need to.
If we are looking purely at taste, the best burger hands down in the Shack Stack from Shake Shack. It is a normal burger with an added fried cheese stuffed portobello mushroom. So basically bun, lettuce, tomatoes, fried cheese stuffed portobello mushroom, patty, bun. It is a monstrously awesome burger. You have to be very careful with this burger because if you eat it the wrong way you can shoot the cheese out of the portobello mushroom on to your face and the cheese is really hot. The main downside is that this burger is pricey, if you want a cheaper alternative you can just get the mushroom burger which is basically the same burger without the patty.
As you may have noticed I haven't mentioned Five Guy's burger; this is not to say that it is a bad burger. Their burgers are really good, but when compared to Shake Shack and In n Out, it is their fries that shine.