I've had my 21" Lawn-Boy Gold push mower (no sissy self-propelled for me, thank you) since 1996. I did have a bad ignition coil fixed under warranty, but that's it. I think I've changed the plug once, and clean the carbon from the muffler every few years - never much in there anyway. I either clean or replace the air filter every year. I like the two-pack of pre-oiled Lawn-Boy filters, but they sure rape you for $.25 worth of foam. At least your hands don't smell like gas for 2 days after cleaning the old one....
I don't know that 2-cycle is any better or worse than 4-cycle. Previously I had an old Toro (mid 80's) with a Tecumseh on it. I mowed my yard in high school with it. I went to visit my parents around '95 and my dad pulls it out of the shed. It hadn't been run in years, but at least he ran it dry prior to storage. We poured a splash of fresh gas in it, checked the oil, and it fired right up. I took it home and mowed with it for several years before I bought the Lawn-Boy. The Toro was only an 18" cut, and also designed to bag, not mulch or discharge. I don't bag, and 18" wasn't enough for our lot. But it always ran perfectly.
I think it boils down to maintenance. A two-stroke only needs a plug once in a while and a clean air filter. They will run and run. Finally they carbon up and you need to pull the muffler off, and maybe by then it's due for rings anyway. A four-stroke needs regular oil changes with the proper oil and also the level checked. Most also require the valve clearance be checked after a lot of hours because they will get too tight and burn them (at least the flat head engines will). Air filters and plugs are same as a two-stroke.
Lastly, engines today are cost-reduced, emissions-choked junk. Many, if not most, pushmower engines are Chinese, especially the big-box store disposable mowers. There are still premium engines, but you pay for them.
I wish I'd had the forethought to pick up a Lawn-Boy Commercial mower just before they switched to the Dura-Force engine. I like the old "F" engine design better. The Dura-Force run well once you tweak the carb jetting, but stock, many of them are horrible "surgers", but either way, there's nothing like the smell of two-stroke exhaust and fresh cut grass on a summer day....... except maybe burning coal on a winter day!