I prefer a multi-pronged approach to my food preps.
First off, I'll say this, you really shouldn't prep "emergency" food that you don't normally eat. The reason is that the last thing you want to do in a crisis is have to deal with the stomach issues arising from getting used to new foods.
STORE BOUGHT CANNED FOOD - this is just a given. While most are dated for a year, they are still perfectly safe up to 5 years or more. The taste may change a little (especially for canned fruit) and you may not get as many nutrients from some, but most canned foods will still be fine for this time. Some different things to think of too: canned evaporated milk, or even dry milk. Can also get dry butter.
HOME CANNED FOOD - This will last WAY longer than the above, and still retain taste, nutrients much longer. This is also a great way to handle the harvest from the next option (the home garden). There is some up front cost here (pressure cooker, canning supplies, etc.) and some learning to do, but for prepping, you just can't beat this at all. Note, there are some different types, so need to be educated on this, but a lot of material out there to help.
HOME GARDEN - you don't need acres for this. Many foods can be grown in pots, even hanging baskets. Fruit trees also fall into this category. This is just great, renewable food. Besides, with any extra, you can do the above for long term storage (canning).
DRY GOODS - These items keep for up to 15 (some say 20) years. Things like dry pasta, mashed potato flakes, dry cereals, dry rice, dry grains, dry beans, flour, sugar, popcorn kernels, and dry corn are great, and can be stored in tightly sealed containers to keep well. You may need desiccant packs for some of these, to absorb any moisture that forms. These things are hard to make yourself, so a good idea to stockpile, and rotate through. Again, food you are used to eating anyhow. (and don't forget dried spices, though you should be growing some spices too).
COOKING ESSENTIALS - These are things like cooking oil, seasonings, bullion, sauce mixes, condiments, bottled sauces, etc. While not a "need", I'm more about preserving a certain quality of life vs. just survival.
With all or even some of the above, you should be set just fine. But, you don't have to do it all at once. It's a process. Can build up.
