Factors to consider...
 

Taste— Eat what you like. Don't try and convert your taste buds to new types of food deep in the       back country.

Calories— Don't inaugurate a diet program during a multi-night hike. You'll need ample calories (and water!) to fight off fatigue and headaches.

Nutrition— It's fine to tear into a candy bar during a trip, but for the long haul you want to rely on complex carbohydrates and proteins. Intelligent quick-eats such as nuts and dry fruits provide a stable flow of energy to your muscles.

Weight and Bulk— Stick to lightweight and low bulk foods as much as possible, especially on long journeys.

Ease of Preparation— Unless you are an experienced gourmet, keep things simple. It's smart to be well supplied with no-cook food items in case your stove malfunctions.

Cost— Convenience has its price. Freeze-dried meals and energy foods can be expensive, but at the end of a long day when your weary body only has enough energy to boil water, such luxuries seem justifiable.

Fresh foods are good for 1 day inside your pack, maybe 2. Carrots can sometimes last longer.

Canned foods sometimes have a place in your pack if the trip is short. Tins of tuna or other canned meat products can be a nice toss-in item.  Skip foods packaged in traditional 15-ounce (or larger) cans. The weight and bulk just aren't worth it.

Dry foods (pasta, noodles, instant rice, soup mixes, drink mixes) are light, take up minimal volume inside a pack and offer you some decent taste alternatives.

Freeze-dried/dehydrated foods have improved considerably in taste, texture and appearance in recent years. They cost about the same as a meal at a modestly priced restaurant.

Spices can be crucial to boosting the appeal of back country food. Consider
bringing your own spice kit.

Flavored beverages can taste mighty refreshing after a few days of nothing
but water. Powdered drink mixes are a nice mid trip treat.