A few things are well borne in mind regarding power outage prep:

The only sure benefit of a backup power system is a reduction in
worry, which accrues regardless of use. 

Replicating utility service is unlikely to be feasible, if only
on grounds of fuel storage, so compromises are inevitable and
somewhat tangled.  

For most folks, outages are rare.

Most outages are brief, minutes or hours, not days.

With rare exceptions, brief outages are harmless.

Most continuous electrical loads are small. 

Gasoline consumption for small generators is roughly
.1 x (nameplate kW + load kW) gallons per hour.

Induction motorized appliances typically have a momentary peak draw 10X 
average draw. Examples include airconditioners, pumps and refrigerators. 

Fuel supply tends to be the most difficult and expensive part of 
electrical backup preparation, potentially more so than the generator
if the endurance desired is more than a day or two in a populated
area. Out of town, it's expensive to store much fuel but in town
it might very well be prohibited. Piped natural gas is best in that
regard.

Loads that are worth backing up are apt to be scattered among many circuits.
Fridge in the kitchen, freezer in the garage, Internet in the study or den.
Furnace in the basement or a closet.

One can infer that fuel storage and power distribution are likely 
to be the most vexatious problems to be solved. They are site
specific and subject to building codes if permanently installed.
Temporary measures (gas cans and extension cords) are very inconvenient.

I'd suggest starting with putting uninterruptible power supplies on the
items of greatest interest, in my case communications and food storage.
Sized to give a few hours' endurance, that will cover the vast majority
of outages, with the UPS picking up the loads before it's noticed. The
beer stays cold and Google is always available.

Short of the most elaborate configurations, continuous generator operation
isn't realistic: At a minimum the generator has to be shutdown to check oil
levels about once per day. Having UPS units on small, continuous loads will 
allow the generator to be shut off to minimize noise and fuel use. Bear in 
mind, fuel gets scarce very quickly in widespread, long-duration outages. 
Most gas stations can't sell fuel even if they have it unless _they_ have 
a backup power supply. Few do.

By starting with UPS units, you'll cover the most common problems at a cost
roughly comparable to that of a small portable generator but with greater 
convenience. Neither you nor the loads will notice the outage.  No generator 
can start cold and pick up a load in less than a few seconds, meaning 
computers and other comms equipment is guaranteed to crash without a UPS. 
With a UPS, there's no interruption in the first place. If the outage 
approaches the endurance of the UPS there's ample time to start 
the generator. In either scenario the UPS serves a valuable purpose.

Note that the term UPS is widely used for low-capacity devices intended
to permit only a graceful shutdown, not continued operation, of equipment.
What's needed for backup is considerably different, with an order of 
magnitude (at least) greater endurance under normal running load.

If you decide a generator is worth getting, I'd begin by solving the
fuel and wiring problems first. A generator interlock with inlet 
receptacle on your breaker panel is a fairly easy choice, but fuel
really depends on outside circumstances. If you have gasoline lawn care
equipment, gasoline is the obvious choice. If you have a propane grill,
propane is at least worth considering. If you have piped natural gas
that's probably the best option, but the hookup cost will be steep, 
easily more than the generator. On-site bulk propane is good, but
beware of how fast generators use propane, and delivery limitations.
 
This sequence of reasoning is the exact opposite of what I did: I started 
with the generator, then bought extension cables, then settled on using the 
gas in my car as a fuel supply. Only then did I appreciate the worth of a UPS.

Each decision will impact the others, so you'll have to start by setting
goals and estimating costs, possibly several times, before being satisfied. 
For many years "don't worry about it" was a perfectly reasonable approach. 

As the grid ages, that becomes less true. 
 
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