All comes down to what you want to run.
If you plan on only using it for battery charging and running a TV/satellite/game console, i would recommend what others have. get a pair of cheap ~2000w inverter generators capable of paralleling.
for the most part, just running a few small appliances its going to be quiet, and not burn a load of gas. If you feel the need to run an A/C or the ol ladys hair dryer and curling iron (LOL) you can flash up the second generator.
Also like mentioned, 4000w isnt going to run everything, but its going to run quite a bit of gear. If you are going to need to run more than one A/C, your going to have to step up your game.
Id also like to clear up something that was stated incorrectly earlier. An inverter generator is the best option when running sensitive electronics (tvs, laptops/computers/ game consoles, ect). Inverters produce 'clean' power, whereas the typical brushless generator produces a more 'dirty' power as the power supplied to the load is direct from the alternator, not run through an inverter or conditioner. This has absolutely nothing to do with the voltage and whether or not it has a voltage regulator. All generators have a voltage regulator!
If sound is going to be an issue, your options are pretty limited on a conventional generator unless you want to lug around an insulated box to put over it so your neighbours dont bust your knee caps with their baseball bats
. I havent seen a conventional generator regardless of size, that i would personally like to hear running all day in the campground! but if cost is an issue, unless you can find a smoking deal on a pair of small inverters or a large one, its ALOT cheaper to go with a conventional generator (comparing apples to apples here locally its $570 for a conventional style 4000w champion, whereas its $1500 for a pair of 2000w champion inverters, not including the cost of the parallel kit).
another thing to consider too, is fuel cost. If you want to have power all the time, and dont necessarily need alot of power, this is where having the small inverters will shine. you can run one inverter and burn ~2gal a day instead of burning ~8gal a day and having to listen to the conventional generator making a racket all day for nothing.