As one of the oldest stations (if not the oldest) in the country still in use, it does deserve to be better looked after. But the early 19th century architecture is graceful and characterful. Like most stations first out from a major terminal, it has a slight sense of being overlooked by those heading for greater things – compare Manors, Westbourne Park as was, and (more than slight) Ardwick. The area it serves is rather run down though improving; and the access ramp from the street is dispiriting. But it could be revived; it would be much better served and used if Merseyrail took it over.
As for favourite stations, there are too many! But my local Cressington deserves a mention: Victorian gothic like a country vicarage or a school. One of my favourite large stations is (London) Waterloo, which doesn't seem all that popular but to me is full of urban bustle and despite (like most city termini) being now half shopping mall is still identifiably a railway station, unlike Euston or those dreary stations like Charing Cross and Victoria that have built over the platforms. York and Newcastle deserve to be in the top half dozen too. As for Art Deco/ modern, Surbiton has been mentioned: there's also Wimbledon and Richmond. Of course the Holden Piccadilly Line stations, Sudbury Town, Arnos Grove etc. And Merseyrail's (well, the LMS really) homage to these, Hoylake.