Delta's original widget livery is one of the best IMHO, even though I have a thing for Delta; its iconic too, 30 years, I think thats longer than most...

I also think that the United Livery (pre-tulip) was better than the tulip ones. Pan Am's livery was good, and TWA's jet liveries were cool too. I also think that the Boeing yellow and brown liveries were cool. However, some modern ones are better than their airline's old ones. KLM's Blue top is better than the old one, same with Cathay Pacific, British Airways and Aeroflot.