The best burger I've had was at Slater's 50/50 in LA. There's a few locations (mostly in OC) but they just built one in Pasadena

The 50/50 patty, which they are known for, is made up of 50% ground beef and 50% ground bacon. From there, you can dress it any way you want. They have custom burgers or a build your own.

Furthermore, if you are a bacon person, they have lots of bacon options..
Bacon Ketchup
Baconaiise
Bacon Milkshakes
Bacon Bourbon
etc.

My co worker buddy swears on Golden State Cafe but I have yet to try it. The last time I tried to eat there, I got caught up in traffic as there was a big event nearby.

For a fast food burger, I like In n Out fine enough (animal style) but I would agree that Five Guys is better overall.