I have a lot of experience of end users and they are forever telling me that they get so many different "Update this", "Update that" windows that they can no longer distinguish real from fake. Some of them have been tricked by fake web site pop-ups as a result, others ignore legitimate update messages. I do not blame them.
Internet Explorer and Google Chrome get updated in a way that most end users find to be simple to understand, particularly with Chrome. Firefox is also quite good in this regard. All of them are reliable - it is rare, IME, to come across a Windows Update, Firefox or Chrome instance which is silently failing to update. Or not even bothering to prompt to update.
Flash, however often I install it, just doesn't seem to auto-update reliably. Quite often it only does so after a user log on/reboot, which doesn't happen much in the days of standby. Even on brand new, fresh Windows installs (so we know the OS/Flash isn't broken), I test Flash from time to time and it just doesn't prompt to update at all on some occasions. This is what makes Adobe's poor track record exponentially worse - that their software update mechanism is crap at best.
I was gobsmacked when Microsoft declared they were going to start updating Flash via Windows Update. Gobsmacked and so very relieved. It felt like they'd walked into Adobe's office, grabbed their fire extinguishers and told them "You are so useless that when there's a fire, WE will come and put it out, since you don't seem able to. We are sick of our offices getting burned down because of your idle incompetence."
I won't even address Oracle's Java. Bundling malware with their updater is tantamount to crime.