Vanilla is better than chocolate because it has a more smooth and light taste, and it tastes wonderfully delicious. If your a milk lover, vanilla is the flavor for you. But chocolate has a crispy taste that doesn't really taste good in some kinds of ice cream. I'm not saying it's bad, it just doesn't really fit the needs of a delicious ice cream flavor like vanilla.
If I were eating just a regular cone of ice cream, vanilla would not be my first choice. It tastes good, but it's generic. The plainness of vanilla, however, is where it's true strength comes from. While which ice cream flavor someone likes the best is, obviously, subjective, I believe that there are many points that can be argued in vanilla ice creams flavor that do not apply to other ice creams. For one thing, it is the easiest ice cream to make. All you really need to make somewhat decent ice cream is a large plastic bag, a small plastic bag, some ice, salt, cream, and whatever flavoring you want to use. The salt and ice are easy enough, and cream is something that you might need to buy but might also randomly have lying in fridge for some long forgotten reason. Either way, it's fairly easy to find. If you're making vanilla ice cream, all you do is throw in some vanilla extract, which is something you'll have if you've ever done any baking, which you probably have if you're willing to put time into making ice cream instead of buying it like a normal person, and you're done. You might also need sugar, probably but I don't know. If you want to make other flavors, I have no idea how to help you with that.
Vanilla is also the most suitable ice cream for sundaes. It's unobtrusive flavor allows for a greater mixing of things on it. Vanilla for ice cream is like the color black is for clothing. It goes with pretty much everything. With other flavors, however, unless you're under the age of ten and are completely okay with putting anything in your mouth as long as it contains copious amounts of sugar, you need to think about what you're putting on your sundae in order for it to not taste like a complete mess.
No matter how much you put on top of the vanilla icecream you cannot get a flavorful enough icecream as if you just started out with chocolate or whatever other flavor you were going for. If vinilla is your favorite then that means its your least non-favorite in which case you just don't like icecream.