We need and use our genny as needed, but we prefer boondocking and dry camping. Primary function of our generator is to run AC, microwave, and other high current draw items. More than 90 percent of the time we use our PS inverter to provide 120 volt AC power for our laptops, charging phones/tablets, and onboard audio/video equipment. Our solar does a great job of replenishing our battery bank most days, seldom does inverter usage cause our 12 volt reserves to drop anywhere near 50 percent.
It appears you haven't needed a generator thus far and unless you have plans to drastically change the way you use your RV it could sit unused most of the time. Onboard generators are very costly and will suffer issues from non-use, might not be the wisest route to take. Our Onan has served us well over the last 9 years but it gets plenty of use and I do all the maintenance.
Since you have not had a generator along in the past a portable inverter generator will give you access to 120VAC power while not breaking the bank compared to factory installed units. Inverter generators offer quiet operation and fuel savings over open cage and onboard versions. An assessment of your total power requirements at any given time will be needed to properly size your choice.
These examples are rough estimates, a 2000 watt genny will power most item(s) in your rig with the exception of the AC unit. A 3000 watt genny will power a single AC unit but won't power the microwave or other high draw items at the same time. A 4000 watt genny will completely power most 30 amp rigs, 5500 and higher wattage units are needed to entirely power a 50 amp coach.
We love the independence of having a generator that allows us the freedom to run our rig as if we were plugged into shore power, although circumstances commonly occur just a few times a year. We often camp in extreme weather and having full function of all our RV's amenities when no hookups are available can be priceless, peace of mind is what it's all about. We recently added a Champion 3100 remote start portable unit to the mix since the Onan is way overkill under most operations.