I know some people out there swear by chocolate based ice-cream; chocolate ice cream with fudge brownies, chocolate ice cream with caramel swirl, etc. I think that – and hear me out on this – chocolate is much too rich and overpowering a flavor to allow the other tastes to be fully enjoyed, to the point where all you savor is the chocolate. Chocolate toffee ice cream? Nope, just tastes like chocolate. Chocolate ice cream with cookie dough? Nope, only chocolate. Chocolate overwhelms the palate and will often ruin the entire flavor.
Vanilla, on the other hand, is sweet and creamy yet not too rich, meaning that it allows other flavors to shine. Cookies and cream, cookie dough, etc. ice creams all have vanilla bases.