Someone asked this before recently so I'll reiterate the answer I posted then:
It really depends on what type of content you make, and what your goals are.
If you make super high quality animations that take like 10-20+ hours to make, you're probably only going to be coming out with one video every week or two, maybe even every 3-4 weeks or less if it's just a hobby for you and not full time - but those videos are likely getting shared a ton, and going viral, so as far as you're concerned, the total viewership will be the same or greater. As for the regulars on your channel, they've come to expect these high quality clips, so they won't mind waiting a few weeks for the next one.
If you post for example gaming videos, then that's more an every day type of entertainment. Lots of shorter clips, taken from hours of gaming. It's kind of expected that there should be new videos from you every day, ideally multiple ones because not everyone likes the same games - so if you only have one clip from one game out that day, a % of your audience who don't like that game will have nothing to watch.
Most people fall somewhere in between those, i.e. you should be posting new videos every week, but even just 1 or 2 a week will usually be enough.
That said, if YouTube is at all something you do for monetary reasons, or your channel is something you want to grow, you should consider making videos as frequently as possible. The more videos you have up, the more chances of you ranking in search/suggested videos. That means more views, and more ad revenue. The more views, the more people discover your channel in the first place too, so the more people who may invest in your products if they're something that could be helpful to them etc.
Now that's quantity covered, but what about quality? Well, again it depends a lot on what you're doing:
If you're gaming, the video quality, audio quality from your mic, and entertainment value should be all top notch - but if you don't have flashy editing, or you suck at the game, or something else - that doesn't really detract from it all that much.
If you're making self-development oriented videos like me, then the most important factor is the quality of information you're giving - audio quality or video quality or other aspects can be sacrificed as long as the information is good and the lessons are understandable, since that's the primary value such a channel offers.
If you're making those animations I mentioned earlier, then because such a long time is spent on them to begin with, you're kind of upheld to a higher standard quality wise.
So it all depends, but a general rule of thumb for all channel types is: Upload as frequently as you can, without compromising the value that your channel offers.
The value that your channel offers is what people come to your channel for. For a gaming or comedy channel, that's to be entertained. For a self-improvement or tutorial channel, that's to learn something new. For an animation channel, that's to watch something that looks cool. etc.
