Old question, but common problem.
There IS a sensible, safe, legal middle ground between backfeeding and a full-blown (and expensive) transfer switch: a circuit-breaker panel interlock switch.
An interlock is basically a special set of two pairs of linked circuit breakers that install into your existing circuit breaker panel:
The breaker pairs are designed to physically prevent you from connecting the panel to the generator unless you've already flipped the other pair of breakers to disconnect it from utility power.
An interlock is a fantastic solution if you have a relatively new panel capable of supporting an interlock (most new ones can, though you might have to buy the actual components to do it online... Home Depot & Lowes sell compatible panels, but AFAIK, don't normally keep the interlock components in stock). If you have an older panel, or a more complicated setup (say, a maxed-out panel with one or more additional subpanels), you might have to consider other options... but for most people, an interlock is a great option.
There is one "gotcha" to keep in mind -- to power everything in your house "normally" from a generator, the generator has to be capable of outputting 240v (as split-leg 120v+120v). More importantly, your generator won't run efficiently unless both legs are reasonably well-balanced & drawing approximately equal amounts of power (ie, if you put two window air conditioners and the refrigerator on one leg, and use the other leg to run some lights and a TV, your generator is going to have to work almost twice as hard as it would if you had the big air conditioner on one leg, the small air conditioner and refrigerator on the other leg, and the remaining stuff somewhat well-distributed between the two). With an imbalanced load, the generator basically has to work hard enough to power the larger of the two legs, and just wastes the extra power not used by the other leg.
I think you could still use an interlock with a 120v generator, but none of your 240v appliances would work, and only half the circuits in the house (those connected to one leg) would be powered. You might have to shuffle around a few circuits from one leg to the other in order to make sure that all the outlets you care about would be powered up.
WARNING: before moving circuits from one leg to the other, MAKE SURE the circuit doesn't share a neutral wire with ANOTHER circuit (and that each circuit is connected to a different leg). This is COMMONPLACE, and was considered to be TOTALLY ACCEPTABLE until AFCIs forced a rule change (AFCIs need dedicated neutral wires to work). When two circuits connected to opposite legs share a neutral, their return loads partially cancel each other out, so the neutral wire ends up carrying LESS current. When two circuits connected to the SAME leg share a neutral, their return loads COMBINE (potentially exceeding the wire's rated limits).
The key thing to remember is that generators are NOT "plug and play", especially when temporarily integrated into your home's electrical system. You HAVE to be at least somewhat aware of your home's electrical topography and the amount of power being drawn at any given time from each leg.
A big whole-house diesel or natural gas generator (like those sold by Generac) and automatic transfer switch lets you (mostly) get away with ignoring those technical details by virtue of its sheer brute size, especially if you're wealthy enough to not care about fuel costs.
With a medium-sized portable generator (4800W-7500W), you HAVE to keep those details in mind, or it won't run efficiently.
With a small generator (2500W-4800W), you have to keep those details in mind, or you'll have constant problems with the generator stalling, overheating, and wearing out prematurely (or outright breaking down).
With a really small generator (<2500 watts), you have to be intimately aware of those details, and actively manage your power usage at all times. Personally, with a REALLY small generator, I'd stick to extension cords, if only to constantly remind you that you're dealing with a limited resource that can't be taken for granted and requires constant attention.