I haven't tasted cola in years; back when I drank it I believed I could tell the difference but today I doubt I ever could. I can tell a pilsner apart from a stout. All whiskey tastes like whiskey, but whiskey doesn't taste like gin.

I don't believe I have an impaired sense of taste. I'm just highly skeptical of the objectivity of my sense of taste. Marketting and branding probably has more influence than anything else when comparing two drinks in the same category (wine-to-wine, coffee-to-coffee, etc.)