The poll seems a bit limited - you can't really have just one favourite maunfacturer as many really good manufactirers don't build stuff in all sectors of the market.
Overall I've voted for
Life-Like - their P2K range has really pushed other manufactuers to better quality models for both engines and freight cars in the last 12 years or so.
In individual sectors of the market I'd say there are different leaders:
Diesels: it has to be Life-Like P2K; they are very finely detailed and run real smooth. They also are very good value for money, you can pick a P2K engine up very cheap, and I'm just talking new from a trader or Hobby Store not the second hand deals on Ebay... I'd say Atlas would be a close second. Their stuff is great (I love my Master Series GP38), but its expensive and stays that way.
Steam locos: I'd have to go for Bachman Spectrum; bang for buck you can't beat them.
Freight cars; I like anything I have to put together myself! At the shake the box end of the spectrum it would be Accurail and at the detailed end Red Caboose or P2K.
Passenger cars I love the new Walthers cars, but also like the IHC cars for their value for money. How can you argue against $8 for a car, even if you have to re-work it a bit?
Track; Micro-engineering - no question
Structures Walthers - again no question about it. Their range of Cornerstone building kits just can't be beaten in terms of prototypes chosen and value for money - even if its just the start for a kit-bash!