I always thought the LMS Wirral, Southport and Ormskirk stock of the 1930s was years ahead of its time in appearance and certainly far more stylish than contemporary Southern emus or the LMS's own slam-door stock on the Watford and North London lines. Unfortunately ride quality wasn't always as good.
I remember seeing a picture of the Wirral stock in a book when I was a kid, and thinking how modern they looked compared to the Southern EMUs of their time.
One thing that's long puzzled me about the Southern EMUs is why one group of them, the prewar 6-PAN, 6-CIT and 6-PUL, had considerably fewer jumper cables dangling on the driving ends compared to the other Southern electrics of that time (some pictures
here). This gave them a much cleaner appearance.
I agree with others here in saying that what is attractive is a subjective matter, one of personal aesthetic taste. Having said that, I do think that however ugly some old EMUs were, there are some right ugly ones amongst the modern ones too, such as the
385 class, which (being a Londoner) I'm glad are kept a long way off in Scotland; I wouldn't want one of them to turn up at my local station.