IMNSHO, the secret to a good burger is moderation. Going overboard in any direction is a mistake.
A nice .25-.33 pound patty. Not too thick, not smashed thin. Grilled to medium. American cheese (maybe swiss or muenster). A dallop of mayo, a little bit of ketchup or mustard. Some onions (vidalia are best, grilled is nice but not required). One slice of tomato. One or two lettuce leaves. Maybe a little pickle.
From there, if you want to add anything, you've gotta take other things off. Avocado, sriracha, mushrooms, bacon, peppers, or BBQ sauce all work, but you have to compensate by removing other items and/or sauces. It's a burger, not a salad. And you have to let the flavors come through instead of making them compete with each other - especially the flavor of the meat.
I wish more people took this advice to heart. An overstuffed burger is pointless to me. I think the reason we see so much of it is pure marketing. Got to have a burger description that one-ups the competition and blows you away with the extravagance of it.
I have two go to combinations for basic everyday burgers. The first is mayo, dijon mustard, sweet-hot pickles, and tomato. The second is BBQ sauce, cheddar, bacon, lettuce, and raw onion sliced fairly thin.
But my ultimate burger? The one that I make if I want to use 100% of my power?
Let's do this.
Burger seasoned with salt and freshly ground black pepper, applied before cooking. You should do this for all burgers, but I'm calling it out here just in case someone doesn't know this is important.
Bacon
Homemade BBQ suace - something that is more tangy and spicy rather than sweet.
Caramelized Onion
Cheddar Cheese
Parmesan Cheese Frico - This is grated parm that is cooked on a non-stick surface until golden brown and crispy.
Lettuce sliced very thin and seasoned - Finely slice the lettuce into thin strips, coarsely chop some parsely, mix together with a simple dressing made with lemon juice, olive oil, salt, and pepper. The dressing needs to be very light, we're just seasoning the lettuce here.
I need to do some more testing for the bun, but something yeast risen and with some structure to it.