>>85996300A good webcomic, or at least one that has a good following, has the right combination of writing, drawing, and consistency. There have been comics that have horrible writing, but are cute, and update. There have been stick figures, 8-bit, and copy-paste comics that people have enjoyed. You can be a brilliant writer and great artist, but if you don't update, traffic will be in the single figures a week.
Really, updates are your biggest asset. Look at Garfield, which hasn't been funny since 1980, and you can have random panels put up, and people will still read it.