This is a matter of personal choice. Tastiest is usually fresh but is most complex to prepare, heavy, and requires washing up and doesn't necessarily keep well! Boil in the bag meals are very good but can also be heavy. They require app 8 to 10 minutes boiling to prepare but can be eaten cold. Boiling for this amount of time means that you will use more fuel for cooking than if you used dried food. Freeze dried is the lightest to carry, quickest and easiest to prepare. With modern meal packs you do not lose flavour, though it is essential that the right amount of (boiling) water is used and it is well mixed and left to stand according to the instructions, typically around 5 minutes. Freeze dried meals are often available in 800 calorie packs. Most others have around 300 to 400 calories. Fine for a day or two, but for an extended period away the extra calories will be needed unless you are on a diet. You will probably be needing upwards of 3,000 calories per day on a hiking expedition, and probably more in cold weather. Antarctic treks may need up to 11,000 per day!
A good breakfast is very important, and can reduce the amount you want to eat during the day. My preference is for a boil in the bag breakfast.
Some comfort or reward/treat goodies make a big difference. Those with a high glucose content can provide an instant lift, and can usefully make up an emergency meal pack - just in case you are late back at the end of the trek.
The Robertson's range of concentrated drink mixers take up very little space and can be used to help make up juice drinks for use during a walk. This also minimises the need to stop and boil water, saving gas and time (though time is usually not an issue), especially if it is wet when you don't really want to unload a rucksack just to get a stove out.
Available on-line (and not exhaustive):
Expedition Foods the orange packs above, specialise in high calorie packs 800 or more. Also a wide variety of vegetarian options.
Mountaintrails (not shown above) have a very wide range of excellent packs and also accessories such as powdered butter, pasta and rice fillers, and so on. Also a range of vegetarian options.
Extreme Adventure Foods (not shown above) but supply packs of long-life biscuits as above as well as a very wide range of other freeze dried foods and sundries.
Drinkpac produce self contained sachets of a wide variety of drinks. Less mess, easy to make up.